Allow Group Admins make a GET call for enterprise users
Group Admins are able to use the webapp UI to add managed users to a group. The UI allows them to start typing a username or email address and will return any results that match. If a Group Admin wants to add a member to a group via the API, they need to know a user's user ID. However, GET calls to https://email@example.com by a Group Admin fail with a 403 error. The same call made by a Co-Admin succeeds.