MM-27493 Shared channels (MVP) (#17301)

Remote Cluster Service
- provides ability for multiple Mattermost cluster instances to create a trusted connection with each other and exchange messages
- trusted connections are managed via slash commands (for now)
- facilitates features requiring inter-cluster communication, such as Shared Channels
Shared Channels Service
- provides ability to shared channels between one or more Mattermost cluster instances (using trusted connection)
- sharing/unsharing of channels is managed via slash commands (for now)

config/client.go

@@ -205,6 +205,7 @@ func GenerateClientConfig(c *model.Config, telemetryID string, license *model.Li
 
 		if *license.Features.SharedChannels {
 			props["ExperimentalSharedChannels"] = strconv.FormatBool(*c.ExperimentalSettings.EnableSharedChannels)
+			props["ExperimentalRemoteClusterService"] = strconv.FormatBool(c.FeatureFlags.EnableRemoteClusterService && *c.ExperimentalSettings.EnableRemoteClusterService)
 		}
 	}