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/platform/services/remotecluster/service.go

@@ -68,7 +68,7 @@ type RemoteClusterServiceIFace interface {
 	SendMsg(ctx context.Context, msg model.RemoteClusterMsg, rc *model.RemoteCluster, f SendMsgResultFunc) error
 	SendFile(ctx context.Context, us *model.UploadSession, fi *model.FileInfo, rc *model.RemoteCluster, rp ReaderProvider, f SendFileResultFunc) error
 	SendProfileImage(ctx context.Context, userID string, rc *model.RemoteCluster, provider ProfileImageProvider, f SendProfileImageResultFunc) error
-	AcceptInvitation(invite *model.RemoteClusterInvite, name string, displayName string, creatorId string, teamId string, siteURL string) (*model.RemoteCluster, error)
+	AcceptInvitation(invite *model.RemoteClusterInvite, name string, displayName string, creatorId string, siteURL string) (*model.RemoteCluster, error)
 	ReceiveIncomingMsg(rc *model.RemoteCluster, msg model.RemoteClusterMsg) Response
 	ReceiveInviteConfirmation(invite model.RemoteClusterInvite) (*model.RemoteCluster, error)
 	PingNow(rc *model.RemoteCluster)