Fix "Remove" button in Slack app integration

The data-method attribute was removed by our config of
DOMpurify since we are using v-safe-html. Since this
is trusted input (comes from our own code), we should
allow these attributes for Rails remote link functionality.

Changelog: fixed

app/assets/javascripts/integrations/edit/components/integration_form.vue

@@ -87,6 +87,7 @@ export default {
   },
   helpHtmlConfig: {
     ADD_TAGS: ['use'], // to support icon SVGs
+    FORBID_ATTR: [], // This is trusted input so we can override the default config to allow data-* attributes
   },
 };
 </script>

spec/frontend/integrations/edit/components/integration_form_spec.js

@@ -278,6 +278,7 @@ describe('IntegrationForm', () => {
           <svg class="gl-icon">
             <use></use>
           </svg>
+          <a data-confirm="Are you sure?" data-method="delete" href="/settings/slack"></a>
         </div>
       `);
 
@@ -291,9 +292,14 @@ describe('IntegrationForm', () => {
         });
 
         const helpHtml = wrapper.findByTestId(mockTestId);
+        const helpLink = helpHtml.find('a');
 
         expect(helpHtml.isVisible()).toBe(true);
         expect(helpHtml.find('svg').isVisible()).toBe(true);
+        expect(helpLink.attributes()).toMatchObject({
+          'data-confirm': 'Are you sure?',
+          'data-method': 'delete',
+        });
       });
     });
   });