When processMemberAddEvent bootstrapped a new group DM channel for the
first time on a receiving instance, local users were never notified via
WebSocket — only dm_member_added was broadcast, which requires the client
to already know about the channel. Now, after bootstrap, dm_channel_created
is sent directly to each local connected member, and the redundant
dm_member_added broadcast is skipped for the bootstrap path.
Jannis Braun
8e589f41fd