Add brand templates feature flag

[MAILPOET-5192]

mailpoet/lib/Features/FeaturesController.php

@@ -6,11 +6,13 @@ use MailPoetVendor\Doctrine\DBAL\Exception\TableNotFoundException;
 
 class FeaturesController {
   const LANDINGPAGE_AB_TEST_DEBUGGER = 'landingpage_ab_test_debugger';
+  const FEATURE_BRAND_TEMPLATES = 'brand_templates';
 
   // Define feature defaults in the array below in the following form:
   //   self::FEATURE_NAME_OF_FEATURE => true,
   private $defaults = [
     self::LANDINGPAGE_AB_TEST_DEBUGGER => false,
+    self::FEATURE_BRAND_TEMPLATES => false,
   ];
 
   /** @var array|null */