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/sharedchannel/msg.go

@@ -0,0 +1,43 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package sharedchannel
+
+import (
+	"encoding/json"
+
+	"github.com/mattermost/mattermost-server/v6/model"
+)
+
+// syncMsg represents a change in content (post add/edit/delete, reaction add/remove, users).
+// It is sent to remote clusters as the payload of a `RemoteClusterMsg`.
+type syncMsg struct {
+	Id        string                 `json:"id"`
+	ChannelId string                 `json:"channel_id"`
+	Users     map[string]*model.User `json:"users,omitempty"`
+	Posts     []*model.Post          `json:"posts,omitempty"`
+	Reactions []*model.Reaction      `json:"reactions,omitempty"`
+}
+
+func newSyncMsg(channelID string) *syncMsg {
+	return &syncMsg{
+		Id:        model.NewId(),
+		ChannelId: channelID,
+	}
+}
+
+func (sm *syncMsg) ToJSON() ([]byte, error) {
+	b, err := json.Marshal(sm)
+	if err != nil {
+		return nil, err
+	}
+	return b, nil
+}
+
+func (sm *syncMsg) String() string {
+	json, err := sm.ToJSON()
+	if err != nil {
+		return ""
+	}
+	return string(json)
+}