- Add migrateFixOneOnOneOwnerIds migration to NULL-out ownerId on all
existing 1-on-1 DMs (those with exactly 2 members)
- Fix POST /api/dm to create 1-on-1 channels with ownerId=null instead
of the creator's ID
- Guard POST /api/dm/:id/members: reject with 400 if channel has no
owner (i.e. is a 1-on-1), directing callers to POST /api/dm/group
- Guard DELETE /api/dm/:id/members: replace member-count check with
ownerId check; remove now-duplicate dmChannel query in that handler
- Add CreateGroupDmRequest type to shared types
Jannis Braun
bec4c2446f