Adds Remote Cluster related API endpoints (#27432)

* Adds Remote Cluster related API endpoints

New endpoints for the following routes are added:

- Get Remote Clusters at `GET /api/v4/remotecluster`
- Create Remote Cluster at `POST /api/v4/remotecluster`
- Accept Remote Cluster invite at `POST
/api/v4/remotecluster/accept_invite`
- Generate Remote Cluster invite at `POST
/api/v4/remotecluster/{remote_id}/generate_invite`
- Get Remote Cluster at `GET /api/v4/remotecluster/{remote_id}`
- Patch Remote Cluster at `PATCH /api/v4/remotecluster/{remote_id}`
- Delete Remote Cluster at `DELETE /api/v4/remotecluster/{remote_id}`

These endpoints are planned to be used from the system console, and
gated through the `manage_secure_connections` permission.

* Update server/channels/api4/remote_cluster_test.go

Co-authored-by: Doug Lauder <wiggin77@warpmail.net>

* Fix AppError names

---------

Co-authored-by: Doug Lauder <wiggin77@warpmail.net>
Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/platform/shared_channel_notifier.go

@@ -88,7 +88,7 @@ func handleContentSync(ps *PlatformService, syncService SharedChannelServiceIFac
 			OnlyConfirmed:  true,
 			RequireOptions: model.BitflagOptionAutoShareDMs,
 		}
-		remotes, err := ps.Store.RemoteCluster().GetAll(filter) // empty list returned if none found,  no error
+		remotes, err := ps.Store.RemoteCluster().GetAll(0, 999999, filter) // empty list returned if none found,  no error
 		if err != nil {
 			return fmt.Errorf("cannot fetch remote clusters: %w", err)
 		}