- ChatContext implements golem15.chat's MessageModerator: moderator
group members who are chat members delete in group conversations
only, never in DMs
- GET /chat/embeds?type=deadline|class|reading&q= (members only,
at most 20 rows, escaped ILIKE, q at most 100 characters)
- POST /chat/embeds/resolve {refs} (members only, at most 50 distinct
refs, 8 KiB body): current data or null per ref
