Advanced administration features for rooms

When creating a room admins would be able to:

- Set answerable questions for users who request to join
- Limit how many messages users can send in a row
- Limit how many stickers or media files users can send in a row or within defined period of time
- Ban sending of certain media files or all the media files
- Create customized right sets for people. Right sets could be saved in some kind of right set pack like sticker pack. There could be for example type 1 users: are able to do everything and have admin rights, type 2 users: can send everything but no admin rights, type 3 users: can only send text messages.

No file, test, or entry point is named. Start by mapping the existing room-creation and permission rules in the Matrix specification, then break the requested administration features into a defined scope with acceptance criteria for questions, rate limits, media restrictions, and role sets.

Written by the indexing model from the issue text.