A group's owner sees its members and requests, declines and removes

/clientapi/group had no way to see who is in a group or asks to join it,
so a circle's owner could not answer a request from elsewhere. Now:
- GET /clientapi/group/members: the members (local and remote, with their
  role) and the pending requests, for the group's owner and moderators
  only;
- POST /clientapi/group/reject: declines a request, telling the asker's
  server with a Reject of its Follow;
- POST /clientapi/group/remove: takes a member out (never the owner): a
  persona here stops following the group, one elsewhere gets a Reject of
  its Follow, as Mastodon removes a follower.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub/Controllers/ClientToServer/GroupController.cs

@@ -48,6 +48,18 @@ namespace PrivaPub.Controllers.ClientToServer
 		public async Task<IActionResult> Approve(GroupMembershipForm form, CancellationToken token) =>
 			!ModelState.IsValid ? Invalid() : Answer(await _groupUsersService.ApproveMember(User.GetUserId(), form, token));
 
+		[HttpGet, Route("/clientapi/group/members")]
+		public async Task<IActionResult> Members([FromQuery] string avatarId, [FromQuery] string groupId, CancellationToken token) =>
+			Answer(await _groupUsersService.GetMembers(User.GetUserId(), avatarId, groupId, token));
+
+		[HttpPost, Route("/clientapi/group/reject")]
+		public async Task<IActionResult> Reject(GroupMembershipForm form, CancellationToken token) =>
+			!ModelState.IsValid ? Invalid() : Answer(await _groupUsersService.RejectMember(User.GetUserId(), form, token));
+
+		[HttpPost, Route("/clientapi/group/remove")]
+		public async Task<IActionResult> Remove(GroupMembershipForm form, CancellationToken token) =>
+			!ModelState.IsValid ? Invalid() : Answer(await _groupUsersService.RemoveMember(User.GetUserId(), form, token));
+
 		IActionResult Invalid() => BadRequest(new WebResult().Invalidate(_localizer["Invalid model."]));
 
 		IActionResult Answer(WebResult result) => result.IsValid ? Ok(result.Data) : StatusCode(result.StatusCode, result);