Room membership: joinRoom

[chrisabruce]

Start the requesting user participating in a particular room.

Note that this API takes either a room ID or alias, unlike /room/{roomId}/join.

This API starts a user participating in a particular room, if that user is allowed to participate in that room. After this call, the client is allowed to see all current state events in the room, and all subsequent events associated with the room until the user leaves the room.

After a user has joined a room, the room will appear as an entry in the response of the |/initialSync|_ and |/sync|_ APIs.

If a third_party_signed was supplied, the homeserver must verify that it matches a pending m.room.third_party_invite event in the room, and perform key validity checking if required by the event.