feat(submit): add user media library

tests/widget-system/post-editor-reference-contract.test.cjs

@@ -87,7 +87,7 @@ test('front submit paid resources use the reference modal editor and compact lis
   assert.match(pay, /class="hidden-input"/);
   assert.doesNotMatch(pay, /data-pay-download-upload|data-pay-download-tpl/);
 
-  ['url', 'extract_code', 'copy_key', 'copy_val', 'label', 'class'].forEach((field) => {
+  ['url', 'attachment_id', 'extract_code', 'copy_key', 'copy_val', 'label', 'class'].forEach((field) => {
     assert.match(downloads, new RegExp(`['"]${field}['"]`));
     assert.match(model, new RegExp(`['"]${field}['"]`));
   });