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/store/storetest/mocks/RemoteClusterStore.go

@@ -72,9 +72,9 @@ func (_m *RemoteClusterStore) Get(remoteClusterId string) (*model.RemoteCluster,
 	return r0, r1
 }
 
-// GetAll provides a mock function with given fields: filter
-func (_m *RemoteClusterStore) GetAll(filter model.RemoteClusterQueryFilter) ([]*model.RemoteCluster, error) {
-	ret := _m.Called(filter)
+// GetAll provides a mock function with given fields: offset, limit, filter
+func (_m *RemoteClusterStore) GetAll(offset int, limit int, filter model.RemoteClusterQueryFilter) ([]*model.RemoteCluster, error) {
+	ret := _m.Called(offset, limit, filter)
 
 	if len(ret) == 0 {
 		panic("no return value specified for GetAll")
@@ -82,19 +82,19 @@ func (_m *RemoteClusterStore) GetAll(filter model.RemoteClusterQueryFilter) ([]*
 
 	var r0 []*model.RemoteCluster
 	var r1 error
-	if rf, ok := ret.Get(0).(func(model.RemoteClusterQueryFilter) ([]*model.RemoteCluster, error)); ok {
-		return rf(filter)
+	if rf, ok := ret.Get(0).(func(int, int, model.RemoteClusterQueryFilter) ([]*model.RemoteCluster, error)); ok {
+		return rf(offset, limit, filter)
 	}
-	if rf, ok := ret.Get(0).(func(model.RemoteClusterQueryFilter) []*model.RemoteCluster); ok {
-		r0 = rf(filter)
+	if rf, ok := ret.Get(0).(func(int, int, model.RemoteClusterQueryFilter) []*model.RemoteCluster); ok {
+		r0 = rf(offset, limit, filter)
 	} else {
 		if ret.Get(0) != nil {
 			r0 = ret.Get(0).([]*model.RemoteCluster)
 		}
 	}
 
-	if rf, ok := ret.Get(1).(func(model.RemoteClusterQueryFilter) error); ok {
-		r1 = rf(filter)
+	if rf, ok := ret.Get(1).(func(int, int, model.RemoteClusterQueryFilter) error); ok {
+		r1 = rf(offset, limit, filter)
 	} else {
 		r1 = ret.Error(1)
 	}