This diff implements the same approach as the Farcaster app, where invited users are listed in the members tab and also fixes the issue described in [ENG-11388](https://linear.app/comm/issue/ENG-11388/after-creating-the-farcaster-thread-with-user-which-receives-request).
NOTE:
This solution is not complete; there are two things left, and I won't land this diff until addressing them:
1. There is one `TODO` in this code, I need to discuss with @tomek what the correct approach is.
2. I found some places in the codebase where we rely on the fact that there are only two roles and logic relies on conditions like `!roleIsAdminRole(existingRole)` (which previously was truthy only for members, now also for invitees) - after this, we need to update this and always check for the role we want