`Member.add_user`doesn't detect existing members that have requested access
Member.add_user
should check for an existing access request and remove the requested_at
timestamp to make it a real/active member. Currently, it will silently fail to add the user as a member.
LDAP group sync worked around this temporarily at https://gitlab.com/gitlab-org/gitlab-ee/blob/master/lib/ee/gitlab/ldap/sync/group.rb#L170-174