Do not validate CSRF token in API unless needed

lib/api/api.rb

@@ -48,8 +48,8 @@ module API
     end
     before { header['X-Frame-Options'] = 'SAMEORIGIN' }
-    before { Gitlab::I18n.locale = current_user&.preferred_language }
+    # The locale is set to the current user's locale when `current_user` is loaded
     after { Gitlab::I18n.use_default_locale }
     rescue_from Gitlab::Access::AccessDeniedError do

lib/api/helpers.rb

@@ -16,6 +16,8 @@ module API
       @current_user = initial_current_user
+      Gitlab::I18n.locale = @current_user&.preferred_language
+
       sudo!
       @current_user