API for "Note to self"

[nickvergessen]

• Overview at 📝 Note to self - Overview #2196
• First attempt at 🗒 "My Notes" conversation #3320

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• New conversation type or simply 1-1 with our own?
• Hardcode avatar
• Populate room similarly to changelog conversation

[nickvergessen]

Note-to-self rooms are basically group rooms and the user is an owner, but with the following limitations:

- [ ] Can not add participants to the room
- [ ] Can not allow guests
- [ ] Can not make read-only
- [ ] Can not make listable
- [ ] Can not change permissions
- [ ] Can not set lobby
- [ ] Can not enable SIP
- [ ] Can not configure breakout rooms
- [ ] Can not call