[DISC] Add runtime configuration for OpenHAB (#1658)

* [DISC] Add runtime configuration for OpenHAB

Add an MQTT configurable system key "ohdiscovery" for OpenHAB auto discovery

* Docs and environments update

main/ZmqttDiscovery.ino

@@ -192,6 +192,20 @@ void announceDeviceTrigger(bool use_gateway_info, char* topic, char* type, char*
   pub_custom_topic((char*)topic_to_publish.c_str(), sensor, true);
 }
 
+/*
+  * Remove a substring p from a given string s
+*/
+std::string remove_substring(std::string s, const std::string& p) {
+  std::string::size_type n = p.length();
+
+  for (std::string::size_type i = s.find(p);
+       i != std::string::npos;
+       i = s.find(p))
+    s.erase(i, n);
+
+  return s;
+}
+
 /**
  * @brief Generate message and publish it on an MQTT discovery explorer. For HA @see https://www.home-assistant.io/docs/mqtt/discovery/
  * 
@@ -280,8 +294,13 @@ void createDiscovery(const char* sensor_type,
   sensor["uniq_id"] = unique_id; //unique_id
   if (retainCmd)
     sensor["retain"] = retainCmd; // Retain command
-  if (value_template[0])
-    sensor["val_tpl"] = value_template; //value_template
+  if (value_template[0]) {
+    if (strstr(value_template, " | is_defined") != NULL && OpenHABDisc) {
+      sensor["val_tpl"] = remove_substring(value_template, " | is_defined"); //OpenHAB compatible HA auto discovery
+    } else {
+      sensor["val_tpl"] = value_template; //HA Auto discovery
+    }
+  }
   if (payload_on[0]) {
     if (strcmp(sensor_type, "button") == 0) {
       sensor["pl_prs"] = payload_on; // payload_press for a button press