Filter discovery messages against HASS classes list (#1127)

* Filter the discovery message content against HASS list of classes

main/ZmqttDiscovery.ino

@@ -245,11 +245,20 @@ void createDiscovery(const char* sensor_type,
     sensor["stat_t"] = state_topic;
   }
 
+  // We check if the class belongs to HAAS class list
+  bool HASSClass = false;
+  int num_classes = sizeof(availableHASSClasses) / sizeof(availableHASSClasses[0]);
+  for (int i = 0; i < num_classes; i++) { // see class list and size into config_mqttDiscovery.h
+    if (strcmp(availableHASSClasses[i], device_class) == 0) {
+      HASSClass = true;
+    }
+  }
+
   sensor["name"] = s_name; //name
   sensor["uniq_id"] = unique_id; //unique_id
   if (retainCmd)
     sensor["retain"] = retainCmd; // Retain command
-  if (device_class[0])
+  if (device_class[0] && HASSClass)
     sensor["dev_cla"] = device_class; //device_class
   if (value_template[0])
     sensor["val_tpl"] = value_template; //value_template
@@ -257,7 +266,7 @@ void createDiscovery(const char* sensor_type,
     sensor["pl_on"] = payload_on; // payload_on
   if (payload_off[0])
     sensor["pl_off"] = payload_off; //payload_off
-  if (unit_of_meas[0])
+  if (unit_of_meas[0] && HASSClass)
     sensor["unit_of_meas"] = unit_of_meas; //unit_of_measurement*/
   if (off_delay != 0)
     sensor["off_delay"] = off_delay; //off_delay

main/config_mqttDiscovery.h

@@ -196,4 +196,21 @@ void announceDeviceTrigger(bool use_gateway_info,
 #  define stateClassTotalIncreasing "total_increasing"
 #endif
 
+// From https://github.com/home-assistant/core/blob/d7ac4bd65379e11461c7ce0893d3533d8d8b8cbf/homeassistant/const.py#L225
+// List of classes available in Home Assistant
+const char* availableHASSClasses[] = {"battery",
+                                      "carbon_monoxide",
+                                      "carbon_dioxide",
+                                      "humidity",
+                                      "illuminance",
+                                      "signal_strength",
+                                      "temperature",
+                                      "timestamp",
+                                      "pressure",
+                                      "power",
+                                      "current",
+                                      "energy",
+                                      "power_factor",
+                                      "voltage"};
+
 #endif