Webhooks don't support the threading yet, so this is token only.
In discord you can reply on each message of a thread, but this is not possible in mattermost (so some changes added there to make sure we always answer on the rootID of the thread).
Also needs some more testing with slack.
update : It now also uses the token when replying to a thread (even if webhooks are enabled), until webhooks have support for threads.
An extra avatarMap (cache) is created for mattermost and telegram.
If MediaServerUpload is configured, the avatar images of users are downloaded the first time a
user sends a message.
If this download succeeds a message with EVENT_AVATAR_DOWNLOAD is sent to the originating protocol.
This message also contains a SHA field (in msg.Extra["file"]), if this is not empty, the sha will
be added to the avatarMap. (so we now have a userid-sha cache)
Next time this user sends a message, the MediaServerUpload/sha/userid.png URL will be used as the
avatar field.
Refactor message.Extra to a map[string][]interface{} to have a bit more flexibility
for stuffing extra stuff.
For attached files from slack, files < 1MB size get downloaded (in memory), and get
put into Extra["file"][]config.FileInfo (containing a pointer to the buffer and
the filename). This is not async so slack channels with lots of attached files
may suffer a slowdown. (the download timeout is set at 5 seconds).
Currently fully support mattermost,slack and discord.
Message deleted on the bridge or received from other bridges will be
deleted.
Partially support for Gitter.
Gitter bridge will delete messages received from other bridges.
But if you delete a message on gitter, this deletion will not be sent to
other bridges (this is a gitter API limitation, it doesn't propogate edits
or deletes via the API)
