pub fn clear_dm_pair_key(conn: &Connection, room_id: &str) -> Result<()>Expand description
Free room_id’s dm_pair_key slot (set it to NULL) — called when a
prior DM between the same pair is no longer live (one party left), so a
freshly created room between the same two users can claim that pair key
without violating rooms.dm_pair_key’s UNIQUE constraint. The old room
keeps every other field; only its claim on the pair key is released.