API Deprecate API being removed in CMS 6

src/Forms/GridField/GridFieldFilterHeader.php

@@ -318,9 +318,14 @@ public function setSearchContext(SearchContext $context): static
      *
      * @param GridField $gridfield
      * @return string
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\ORM\Search\SearchContextForm::getSchemaData()
      */
     public function getSearchFieldSchema(GridField $gridField)
     {
+        Deprecation::noticeWithNoReplacment(
+            '5.4.0',
+            'Will be replaced with SilverStripe\ORM\Search\SearchContextForm::getSchemaData()'
+        );
         $schemaUrl = Controller::join_links($gridField->Link(), 'schema/SearchForm');
         $inst = singleton($gridField->getModelClass());
         $context = $this->getSearchContext($gridField);
@@ -424,9 +429,14 @@ public function getSearchForm(GridField $gridField)
      *
      * @param GridField $gridfield
      * @return HTTPResponse
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\Forms\FormRequestHandler::getSchema()
      */
     public function getSearchFormSchema(GridField $gridField)
     {
+        Deprecation::noticeWithNoReplacment(
+            '5.4.0',
+            'Will be replaced with SilverStripe\Forms\FormRequestHandler::getSchema()'
+        );
         $form = $this->getSearchForm($gridField);
 
         // If there are no filterable fields, return a 400 response

src/Forms/Schema/FormSchema.php

@@ -40,6 +40,11 @@ class FormSchema
      */
     const PART_AUTO = 'auto';
 
+    /**
+     * Form schema header identifier
+     */
+    public const SCHEMA_HEADER = 'X-Formschema-Request';
+
     /**
      * Returns a representation of the provided {@link Form} as structured data,
      * based on the request data.