Added 'datetime' to Mqtt Heartbeat Report

This change adds Date and Time ('datetime') to the
Mqtt Heartbeat Report, which can help diagnose the
Mqtt connection and/or client device problems.

Uptime is already reported, but without a datetime
context it is unknown if the retained Mqtt
informantion is current.

Note: Date and Time will not be reported if
NTP_SUPPORT is NOT enabled.

-

code/espurna/config/general.h

@@ -120,6 +120,7 @@
 #define HEARTBEAT_REPORT_MAC        1
 #define HEARTBEAT_REPORT_RSSI       1
 #define HEARTBEAT_REPORT_UPTIME     1
+#define HEARTBEAT_REPORT_DATETIME   1
 #define HEARTBEAT_REPORT_FREEHEAP   1
 #define HEARTBEAT_REPORT_VCC        1
 #define HEARTBEAT_REPORT_RELAY      1
@@ -431,6 +432,7 @@ PROGMEM const char* const custom_reset_string[] = {
 #define MQTT_TOPIC_IP           "ip"
 #define MQTT_TOPIC_VERSION      "version"
 #define MQTT_TOPIC_UPTIME       "uptime"
+#define MQTT_TOPIC_DATETIME     "datetime"
 #define MQTT_TOPIC_FREEHEAP     "freeheap"
 #define MQTT_TOPIC_VCC          "vcc"
 #define MQTT_TOPIC_STATUS       "status"

code/espurna/utils.ino

@@ -118,6 +118,9 @@ void heartbeat() {
         #if (HEARTBEAT_REPORT_UPTIME)
             mqttSend(MQTT_TOPIC_UPTIME, String(uptime_seconds).c_str());
         #endif
+        #if (HEARTBEAT_REPORT_DATETIME) & (NTP_SUPPORT)
+            mqttSend(MQTT_TOPIC_DATETIME, String(ntpDateTime()).c_str());
+        #endif
         #if (HEARTBEAT_REPORT_FREEHEAP)
             mqttSend(MQTT_TOPIC_FREEHEAP, String(free_heap).c_str());
         #endif