In the earlier MR
(https://gitlab.com/gitlab-org/gitlab/-/merge_requests/152584)
we've added the `request_accepted_at` column in the `member` model
to store the user's access granted date

In this MR we expose this field and use it to render the correct
access granted date on the client side

Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/24721
Changelog: changed