Improve room join and history handling

Handling of auto login and adding of room history entries has been removed from components (RoomJoinComponent, RoomParticipantPageComponent. The auth guard is now also active for participant role and handles those things.

As a result, it is now possible to enter the app using any route for participants w/o prior authentication. Furthermore, this fixes duplicate requests to retrieve the room and update the history. The room history is now only updated if the user doesn't already have a membership.

This also adds an event fired when joining a room for the first time to reset locally cached memberships. The room is now shown in the list w/o reloading the app (this was a regression introduces by !624 (merged)).

Closes: #623 (closed)
Related: !624 (merged), !644 (merged), !647 (merged)