Unread ai summary

[SystemKeeper]

• Based on https://github.com/nextcloud/talk-ios/pull/1854

• [x] Needs fixing of (or working around) https://github.com/nextcloud/talk-ios/issues/1381 to work correctly. Done in https://github.com/nextcloud/talk-ios/pull/1886

• [x] Needs database bump

• [x] Respecting nextOffset parameter

[SystemKeeper]

@Ivansss Putting it to review for now, would do the database bump when we decide this is ready.

[SystemKeeper]

@Ivansss Putting it to review for now, would do the database bump when we decide this is ready.

Should all be done now.