Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/platform/services/remotecluster/recv.go

@@ -0,0 +1,53 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package remotecluster
+
+import (
+	"fmt"
+
+	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/server/platform/shared/mlog"
+)
+
+// ReceiveIncomingMsg is called by the Rest API layer, or websocket layer (future), when a Remote Cluster
+// message is received.  Here we route the message to any topic listeners.
+// `rc` and `msg` cannot be nil.
+func (rcs *Service) ReceiveIncomingMsg(rc *model.RemoteCluster, msg model.RemoteClusterMsg) Response {
+	rcs.mux.RLock()
+	defer rcs.mux.RUnlock()
+
+	if metrics := rcs.server.GetMetrics(); metrics != nil {
+		metrics.IncrementRemoteClusterMsgReceivedCounter(rc.RemoteId)
+	}
+
+	rcSanitized := *rc
+	rcSanitized.Token = ""
+	rcSanitized.RemoteToken = ""
+
+	var response Response
+	response.Status = ResponseStatusOK
+
+	listeners := rcs.getTopicListeners(msg.Topic)
+
+	for _, l := range listeners {
+		if err := callback(l, msg, &rcSanitized, &response); err != nil {
+			rcs.server.Log().Log(mlog.LvlRemoteClusterServiceError, "Error from remote cluster message listener",
+				mlog.String("msgId", msg.Id), mlog.String("topic", msg.Topic), mlog.String("remote", rc.DisplayName), mlog.Err(err))
+
+			response.Status = ResponseStatusFail
+			response.Err = err.Error()
+		}
+	}
+	return response
+}
+
+func callback(listener TopicListener, msg model.RemoteClusterMsg, rc *model.RemoteCluster, resp *Response) (err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("%v", r)
+		}
+	}()
+	err = listener(msg, rc, resp)
+	return
+}