Custom Slack client

This change will allow to pass an importable and valid class that will be used to initialize the base Machine class

Missing methods and additional attributes may be created and used.

It defaults to machine.clients.slack.SlackClient if there is no SLACK_CLIENT in local_settings.py

machine/core.py

@@ -119,8 +119,14 @@ async def _setup_slack_clients(self) -> None:
             proxy=self._settings["HTTP_PROXY"],
         )
 
+        # Find out if the default client should be used or a custom one
+        client = self._settings.get("SLACK_CLIENT", "machine.clients.slack.SlackClient")
+        logger.info("Initializing Slack client `%s`...", client)
+        _, cls = import_string(client)[0]
+
         # Setup high-level Slack client for plugins
-        self._client = SlackClient(self._socket_mode_client, self._tz)
+        self._client = cls(self._socket_mode_client, self._tz)
+        logger.info("Slack client `%s` initialized", client)
         await self._client.setup()
 
     # TODO: factor out plugin registration in separate class / set of functions