Interface UIMessage

photo_id on the way in, media on the way back.

It used to be a bare base64 string, which made every attachment a photo by construction — a voice note or a GIF had nowhere to say what it was. media is a projection rather than the whole row for a reason that is not tidiness: a conversation is shared, so embedding the uploader's citizenid would hand it to every other participant. Same reasoning as publicColumns on a public read (§10).

Whether the sender has rewritten this since sending it.

Derived, never stored — MessageRepository.findByConversation computes updated_at > created_at in SQL, off the ON UPDATE CURRENT_TIMESTAMP the column already carries. Optional because a freshly-sent row has never been edited and the send path has no reason to say so.

Who sent this, when it was not a player (MICA-223): the label a resource gave SendMessage -- a business name, or the number it registered. Null, and absent from the wire, for a message a player wrote.

Whether the reader sent this. False for a text from a line, which arrives on their row.

The Participant.id of the member who sent it, in this thread; null for a text from a line and for a sender who has since left the thread.