Plus, heartbeat will send this regardless

For the clean session stuff... when changing configuration of something like RPN,
the old subscription never goes away and we also receive old messages when QoS > 0 is used

Pending changes in the MQTT client(s) to make this work more reliably

- clamp values via helper functions
- unify channel access as long
  slightly more ram, but we no longer cast values that are 32bit-wide anyway
- remove css option, send unconditionally as /hex
- reimplement hsv conversion functions (based on HA / python's colorsys)
  simplify calculations and allow to return standalone value structs for
  RGB and HSV
- named channel accessors
- implement HA color inputs / outputs

get rid of LIGHT_CHANNELS, but keep channel setting for the my92xx
also clean up recent changes, channel command did not actually work

ref. #2423

- retain setting
- generate topic and message in the discovery object instead of
creating them all at once
- re-implement relays, lights and sensors discovery
- rework name normalization, use relative magnitude indexes
- replace original lights code with schema: json, subscribe to a special
topic to handle lights instead of using the common API
(still wip - colors, hs, temperature settings)

resolve #630
resolve #1564
resolve #2403

- shrink utils source file, move heartbeat and boot management into system
- improvise with 'heartbeat' functionality. include scheduler implementation that will
manage the per-module heartbeat callbacks with individual 'mode' and
'interval' settings. current ones are mqtt (including relays, lights, thermostat), debug and
influxdb. preserve heartbeat NONE, ONCE and REPEAT, REPEAT_STATUS is effectively a hbReport & status bit.
- mqtt heartbeat is managed through mqttHeartbeat() callbacks
- tweak mqtt callbacks to use lists instead of the vector, slighly reducing the size of the .bin
- update WebUI, include report setting and update hbMode values
- make sure general.h settings include new heartbeat,
move constant definitions outside of the header
- correctly include dependencies through the .cpp, avoid leaking
internal details.
- as a side-effect, base headers are no longer included recursively

- make sure server is never empty
- disable dhcp option when server *is* empty
- update configure() to detect both tz and server changes

- allow strings in mode (off, on, none)
- fixup type used for the mode to be am enum instead of int
  (todo: allow webui to accept strings?)
- some cli updates using new funcs

update custom action callback to also get the event
buttons fan actions
ifan buttons are handled through action instead of manually
fan settings and api are (sort-of) generic

- gpio module now tracks the known providers (right now, hardware and mcp expander)
- refactored relay struct to use 'Provider' implementing setup,notify,change,boot instead of just BasePin actions
- refactored button module to use gpio provider instead of referencing types itself
- removed dual & stm code from buttons, migrate both to relay module
- added status notify and change callbacks for relayStatus (i.e. 'notify' when relay status was called, but not changed. and 'changed' when it did)  
- relays runtime configuration keys
- relay command now shows configured relays and current & target statuses
- refactor the code using relayStatus(0, blah) under LIGHT_PROVIDER check to use lightState instead
- remove rfbridge code form relay module. implement through a basic state listener in the rfbridge module, depend on RELAY_SUPPORT
- allow to bind rf codes to real relays
- drop tuya-specific lights provider, remove tuya code from relays and lights modules
- integrate tuya via relay listeners and providers, use lights custom provider
- implement channel transitions for tuya. disabled by default, and transition time and step are overridden to 2000 + 100. needs to be set to some value below the total time (i.e. `total transition time / step time == number of steps`, we need to figure out a correct time that serial comms could handle)
- lights custom provider (global, not per-pin) and state listeners
- remove lights code from relay module. implement through providers & listeners in the lights module, depend on RELAY_SUPPORT
- lights per-channel relay provider (unused atm), depend on RELAY_SUPPORT
- refactored channel transition - calculate step only once, make sure time + step values are sane, generate quick transitions with very small delay (10ms hardcoded) for transitions during OFF state i.e. we no longer waste 500ms (or whatever transition time is set to) on boot doing nothing
- transition time + step parameter for the lightUpdate
- report mask parameter for the lightUpdate
- minor fixes across the board

resolve #2222

Port of https://github.com/Vasil-Pahomov/ArWs2812 from Arduino to ESP8266
Implementing garland of WS2812

Co-authored-by: Dmitry Blinov <dblinov@blackberry.com>

- revert hardware.h changes from f497312f29 to
avoid changing existing devices.
- update hardware.h comments related to the _CONFIG and actions

- match paths through a custom AsyncWebHandler instead of using generic not-found fallback handler
- allow MQTT-like patterns when registering paths (`simple/path`, `path/+/something`, `path/#`)
Replaces `relay/0`, `relay/1` etc. with `relay/+`. Magnitudes are plain paths, but using `/+` in case there's more than 1 magnitude of the same type.
- restore `std::function` as callback container (no more single-byte arg nonsense). Still, limit to 1 type per handler type
- adds JSON handlers which will receive JsonObject root as both input and output. Same logic as plain - GET returns resource data, PUT updates it.
- breaking change to `apiAuthenticate(request)`, it no longer will do `request->send(403)` and expect this to be handled externally.
- allow `Api-Key` header containing the key, works for both GET & PUT plain requests. The only way to set apikey for JSON.
- add `ApiRequest::param` to retrieve both GET and PUT params (aka args), remove ApiBuffer
- remove `API_BUFFER_SIZE`. Allow custom form-data key=value pairs for requests, allow to send basic `String`.
- add `API_JSON_BUFFER_SIZE` for the JSON buffer (both input and output)
- `/apis` replaced with `/api/list`, no longer uses custom handler and is an `apiRegister` callback
- `/api/rpc` custom handler replaced with an `apiRegister` callback

WIP further down:
- no more `webLog` for API requests, unless `webAccessLog` / `WEB_ACCESS_LOG` is set to `1`. This also needs to happen to the other handlers. 
- migrate to ArduinoJson v6, since it become apparent it is actually a good upgrade :)
- actually make use of JSON endpoints more, right now it's just existing GET for sensors and relays
- fork ESPAsyncWebServer to cleanup path parsing and temporary objects attached to the request (also, fix things a lot of things based on PRs there...)

- provide a generic way to read default status of the pin after boot
  allows us to use switch as both on and off, independent of the position on boot
- add BUTTON_DEFAULT_LOW & BUTTON_DEFAULT_BOOT (now it's not just BUTTON_DEFAULT_HIGH)
  wiki described raw numbers for some reason :/ this will break that
- clean-up 'constexpr const' and 'const' function args, both are redundant
- clean-up debounce event member defaults, put things in the header

* Add support for Benexmart GU5.3 RGBWW light

* Update arduino.h

Co-authored-by: Max Prokhorov <prokhorov.max@outlook.com>

* Add support for LSC E27 10W white bulb

* Add OTA config for LSC E27 10W white bulb
Add LSC E27 10W white bulb to arduino.h

- Add ::Released button event to be used specifically with switches, opposite of ::Pressed
- Always use default state for switches instead of ignoring it and using current pin reading as value. This allows us to boot with the switch held in the opposite state and trigger the correct event immediately
(meaning, switches now depend on the BUTTON_DEFAULT_HIGH presence to detect the default position)
- BREAKING: Fixup hardware.h. Any custom board needs manual changes.
- BREAKING: Rework MQTT button messages to send text from debug messages instead of numeric code

resolve #2310

also, drop special builds flags in favour of sane defaults

- Buttons events source as button property instead of a global one
- Rename events source -> provider for all settings, consistent with the other things like relay and light providers
- AnalogPin to read between a certain analogRead() range
Trying to follow defaults here - analog 'press' is digital LOW, default value is HIGH, so no additional cfg entries are needed besides pin, level and changing evt source
- (debug) Refactor gpio command, add adc to show analogRead(pin)
- (debug) Add button command

Implemented based on:
https://gitter.im/tinkerman-cat/espurna?at=5f5d44c8df4af236f902e25d
https://gitter.im/tinkerman-cat/espurna?at=5f60e7f1f969413294e95370

Always do digitalRead() after ISR
Drop trigger, since we can handle this inside of reading routine
(although, pending some changes to make reading interval per-sensor)

Rework read / write through std::atomic

- make sure we call run() before checking for errors, we will miss status update otherwise and lock the sensor class in the error state that it cannot recover from
- set error flag only when either bsec or bme680 report an error. ensure we show any issues reported by the library via the debug log
ref. https://gitter.im/tinkerman-cat/espurna?at=5f63a955c1d1a53705abcbe3
TODO: add custom error messages through virtual method?

Also, a minor fix to the sensors test when using 1m and 2m boards

Device in question: https://www.aliexpress.com/item/32925895199.html
Named after print on the PCB.

Co-authored-by: user176176 <>

* Add support for the Zhilde ZLD-64EU-W

This is a power outlet with 6 power sockets and 4 USB ports.

* fixup based on the zld-44eu hw and tasmota template info

Co-authored-by: Maxim Prokhorov <prokhorov.max@outlook.com>

- (experimental) provide generic way to read magnitude values
- expose /api/metrics with values formatted specifically for prometheus, with relay and sensor data
- small tweaks to sensor init

Example config:
```
scrape_configs:
  - job_name: 'espurna'
    metrics_path: '/api/metrics'
    params:
      apikey: ['apikeyapikey']
    static_configs:
      - targets: ['espurna-blabla.lan:80']
```
Where ESPurna side has
```
apiKey => "apikeyapikey"
apiEnabled => "1"
```

* rfb: fix unused repeats setting
* rfb: rename TIMES -> REPEATS
* rfb: use out as first arg

ref. https://travis-ci.com/github/mcspr/espurna-nightly-builder/jobs/378203413#L698

> +env ESPURNA_FLAGS=-DGENERIC_ESP01_512KB ESPURNA_RELEASE_NAME=generic-esp01-512kb ESPURNA_BUILD_SINGLE_SOURCE=1 pio run -e esp8266-512k-base -s -t release
> /home/travis/.platformio/packages/toolchain-xtensa/bin/../lib/gcc/xtensa-lx106-elf/4.8.2/../../../../xtensa-lx106-elf/bin/ld: .pio/build/esp8266-512k-base/firmware.elf section `.irom0.text' will not fit in region `irom0_0_seg'

Remove ~90Kb from the build.

- cache received rfbridge codes in the internal list, allow to operate on it via the rpn operators
- add `<N> <proto> <code> rfb_match`, matching when we receive specified protocol + code string at least N times
- add `<proto> <code> <proto> <code> rfb_sequence`, checking if specified protocol + code pairs happen in sequence
- add `<TIME> <N> <proto> <code> rfb_match_wait` - similar to `rfb_match`, but waiting for at least `TIME` (ms) via oneshot runner
- add `<proto> <code> rfb_info`, pushes code's latest timestamp and it's counter on the stack
- add `<proto> <code> rfb_pop`, which removes the specified protocol + code from the internal cache
- fix MQTT skip setting making RPN variables absent on initial connection
- default to no skip when receiving MQTT
(small issue still stands with us having non-clean MQTT session, broker will persist variable subscriptions even after unsubscribe event)

- RF_... -> RFB_...
- rework rcswitch integration, support variable length payload
- rework rfbridge parser (not tested)
- rework settings scanning routine when trying to match rf payload
  with the relay ID
- update build tests

Remember MAC for the current IP sequence number
(e.g. lease 0 -> xxx.xxx.xxx.2, lease 1 -> xxx.xxx.xxx.3 and etc.)

~500 bytes of code