In this PR:
1. Refactor guards to avoid duplicated queries: WorkspaceAuthGuard and
UserAuthGuard only check for existence of workspace and user in the
request without querying the database
- make member nullable on favorites
- add potential relation with view entity
- add a new type of favorite list in front : workspace favorite
- build a new component for retrieving workspace favorite to display +
refacto the existing one
Bonus:
- removing activities seed since this is deprecated
