Refactor code and improve error handling

Move functions to helpers instead of constants, add unit tests, and improve function to handle cases where there are no inverters or templates to query. Also, remove the dependency on running tests within the main function.

dbus_opendtu.py

@@ -55,6 +55,11 @@ def get_DbusServices(config):
         logging.warning("NumberOfTemplates not set, using default")
         number_of_templates = 0
 
+    # If there are no inverters or templates, return an empty list
+    if number_of_inverters == 0 and number_of_templates == 0:
+        logging.critical("No inverters or templates to query")
+        return services
+
     try:
         dtuvariant = config["DEFAULT"]["DTU"]
     except KeyError:
@@ -158,7 +163,7 @@ def main():
     logging.debug("SignOfLifeLog: %d", signofliveinterval)
 
     # TODO: I think it is better to run the tests inside CI/CD pipeline instead of running it here
-    tests.run_tests()
+    # tests.run_tests()
 
     try:
         logging.info("Start")