Need to include media_url for files M->S to work

[olmari]

If self-hosted appservice-slack is on same server than synapse is, url in config is set to localhost:port, and when media is also bridged there needs to be media_url set in appservice config file like follows (in our server):

homeserver:
  media_url: https://matrix.hacklab.fi
  url: http://localhost:8008
  server_name: hacklab.fi

Without that slackbot gives media/picture-urls as http://localhost:8008/..... to slack which is obvious failure.. But defining media_url resolves this.

ADD/EDIT: So this is first and foremost an documentation issue only, reading source code revealed this is needed and already supported and so on.

[Half-Shot]

This got done.