Users can request to join teams

If a team has `require_join_request=true`, the team view page will display a different ui element or flow for joining the team and would need a new page or ui element for showing moderators which users have requested to join

Start at the team view page and trace how teams expose the `require_join_request=true` setting and current join flow. Define the member request action and a moderator-facing page or UI element for pending requests; done means both flows are represented and the requested users are visible to moderators.

Written by the indexing model from the issue text.