Standardize MQTTDiscovery Temp Keys [deprecate tem key] (#703)

* Detect when sensor isn't available or read fails

* Add temperature conversion macros

* Add 'tempc' & 'tempf' keys to published values

* Unique Values for HA Discovery

* Remove degree symbol from temp sensors

Co-authored-by: Jonathan Michael Wells <jonathan-wells@oist.jp>

main/config_mqttDiscovery.h

@@ -52,12 +52,13 @@ extern void createDiscovery(char* sensor_type,
 #  define jsonFer      "{{ value_json.fer }}"
 #  define jsonMoi      "{{ value_json.moi }}"
 #  define jsonHum      "{{ value_json.hum }}"
-#  define jsonTemp     "{{ value_json.tem }}"
+#  define jsonTemp     "{{ value_json.tem }}" // remove for 0.9.6 release
 #  define jsonStep     "{{ value_json.steps }}"
 #  define jsonWeight   "{{ value_json.weight }}"
 #  define jsonPresence "{{ value_json.presence }}"
 #  define jsonAltim    "{{ value_json.altim }}"
 #  define jsonAltif    "{{ value_json.altift }}"
+#  define jsonTempc    "{{ value_json.tempc }}"
 #  define jsonTempf    "{{ value_json.tempf }}"
 #  define jsonMsg      "{{ value_json.message }}"
 #  define jsonVal      "{{ value_json.value }}"
@@ -77,12 +78,13 @@ extern void createDiscovery(char* sensor_type,
 #  define jsonFer      "{{ value_json.fer | is_defined }}"
 #  define jsonMoi      "{{ value_json.moi | is_defined }}"
 #  define jsonHum      "{{ value_json.hum | is_defined }}"
-#  define jsonTemp     "{{ value_json.tem | is_defined }}"
+#  define jsonTemp     "{{ value_json.tem | is_defined }}" // remove for 0.9.6 release
 #  define jsonStep     "{{ value_json.steps | is_defined }}"
 #  define jsonWeight   "{{ value_json.weight | is_defined }}"
 #  define jsonPresence "{{ value_json.presence | is_defined }}"
 #  define jsonAltim    "{{ value_json.altim | is_defined }}"
 #  define jsonAltif    "{{ value_json.altift | is_defined }}"
+#  define jsonTempc    "{{ value_json.tempc | is_defined }}"
 #  define jsonTempf    "{{ value_json.tempf | is_defined }}"
 #  define jsonMsg      "{{ value_json.message | is_defined }}"
 #  define jsonVal      "{{ value_json.value | is_defined }}"