[BT Discovery] Improve BM2 discovery (#1510)

to filter advertisement coming from iBeacon packets that contains volt
as the voltage is not properly advertised throught the iBeacon packet and render a wrong voltage

main/config_mqttDiscovery.h

@@ -167,6 +167,7 @@ void announceDeviceTrigger(bool use_gateway_info,
 #  define jsonCount    "{{ value_json.count }}"
 #  define jsonAlarm    "{{ value_json.alarm }}"
 #  define jsonInuse    "{{ value_json.power | float > 0 }}"
+#  define jsonVoltBM2  "{{% if  value_json.model_id == \"BM2\" -%} {{value_json.volt}} {%- endif %}}"
 #else // Home assistant autodiscovery value key definition
 #  define jsonBatt     "{{ value_json.batt | is_defined }}"
 #  define jsonLux      "{{ value_json.lux | is_defined }}"
@@ -203,6 +204,7 @@ void announceDeviceTrigger(bool use_gateway_info,
 #  define jsonCount    "{{ value_json.count | is_defined }}"
 #  define jsonAlarm    "{{ value_json.alarm | is_defined }}"
 #  define jsonInuse    "{{ value_json.power | is_defined | float > 0 }}"
+#  define jsonVoltBM2  "{{% if  value_json.model_id == \"BM2\" and value_json.volt is defined -%} {{value_json.volt}} {%- endif %}}"
 #endif
 
 #define stateClassNone            ""