MM-29011: Add feature flag for shared channels (#15585)

* MM-29011: Add feature flag for shared channels

https://mattermost.atlassian.net/browse/MM-29011

* gofmt

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

config/client.go

@@ -59,6 +59,7 @@ func GenerateClientConfig(c *model.Config, telemetryID string, license *model.Li
 	} else {
 		props["ExperimentalChannelOrganization"] = strconv.FormatBool(false)
 	}
+	props["ExperimentalSharedChannels"] = strconv.FormatBool(*c.ExperimentalSettings.EnableSharedChannels)
 
 	props["ExperimentalChannelSidebarOrganization"] = *c.ServiceSettings.ExperimentalChannelSidebarOrganization
 	props["ExperimentalEnableAutomaticReplies"] = strconv.FormatBool(*c.TeamSettings.ExperimentalEnableAutomaticReplies)