Channel banner permissions (#30917)

* Fixed save state panel for channel banner

* Defined default background color

* Updated test

* WIP

* wip

* removed unused param

* Updated tests

* CI

* Fixed mmctl test

* Fixed TestDoAdvancedPermissionsMigration test

* Test update

* lint fix

* lint fix

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/public/model/migration.go

@@ -54,4 +54,5 @@ const (
 	MigrationKeyFixReadAuditsPermission                = "fix_read_audits_permission"
 	MigrationRemoveGetAnalyticsPermission              = "remove_get_analytics_permission"
 	MigrationAddSysconsoleMobileSecurityPermission     = "add_sysconsole_mobile_security_permission"
+	MigrationKeyAddChannelBannerPermissions            = "add_channel_banner_permissions"
 )