Added help message to all cli commands

src/cpl_cli/command/add_service.py

@@ -1,5 +1,6 @@
 import json
-import os.path
+import os
+import textwrap
 from typing import Optional
 
 from cpl.configuration.configuration_abc import ConfigurationABC
@@ -24,6 +25,11 @@ class AddService(CommandABC):
 
         self._workspace = workspace
 
+    @property
+    def help_message(self) -> str:
+        return textwrap.dedent("""\
+        """)
+
     @staticmethod
     def _edit_project_file(source: str, project_settings: ProjectSettings, build_settings: BuildSettings):
         with open(source, 'w') as file: