[SYS] Externalize utils function keep cmpToMainTopic (#2048)

And fill generateHash

Co-authored-by: Florian <1technophile@users.noreply.github.com>

main/main.ino

@@ -820,6 +820,22 @@ void SYSConfig_save() {
 void SYSConfig_save() {}
 #endif
 
+bool cmpToMainTopic(const char* topicOri, const char* toAdd) {
+  // Is string "<mqtt_topic><gateway_name><toAdd>" equal to "<topicOri>"?
+  // Compare first part with first chunk
+  if (strncmp(topicOri, mqtt_topic, strlen(mqtt_topic)) != 0)
+    return false;
+  // Move pointer of sizeof chunk
+  topicOri += strlen(mqtt_topic);
+  // And so on...
+  if (strncmp(topicOri, gateway_name, strlen(gateway_name)) != 0)
+    return false;
+  topicOri += strlen(gateway_name);
+  if (strncmp(topicOri, toAdd, strlen(toAdd)) != 0)
+    return false;
+  return true;
+}
+
 #if defined(ESP32)
 void SYSConfig_load() {
   StaticJsonDocument<JSON_MSG_BUFFER> jsonBuffer;
@@ -3148,7 +3164,7 @@ void readCntParameters(int index) {
 #endif
 
 void MQTTtoSYS(char* topicOri, JsonObject& SYSdata) { // json object decoding
-  if (TheengsUtils::cmpToMainTopic(topicOri, subjectMQTTtoSYSset)) {
+  if (cmpToMainTopic(topicOri, subjectMQTTtoSYSset)) {
     bool restartESP = false;
     Log.trace(F("MQTTtoSYS json" CR));
     if (SYSdata.containsKey("cmd")) {