Show graphql error on confidential mutation

Should have length 0

Added a test

app/assets/javascripts/notes/stores/actions.js

@@ -727,9 +727,13 @@ export const updateConfidentialityOnIssuable = (
     })
     .then(({ data }) => {
       const {
-        issueSetConfidential: { issue },
+        issueSetConfidential: { issue, errors },
       } = data;
 
+      if (errors?.length) {
+        Flash(errors[0], 'alert');
+      } else {
         setConfidentiality({ commit }, issue.confidential);
+      }
     });
 };

spec/frontend/notes/stores/actions_spec.js

@@ -1276,6 +1276,7 @@ describe('Actions Notes Store', () => {
         return actions
           .updateConfidentialityOnIssuable({ commit: commitSpy, state, getters }, actionArgs)
           .then(() => {
+            expect(Flash).not.toHaveBeenCalled();
             expect(commitSpy).toHaveBeenCalledWith(
               mutationTypes.SET_ISSUE_CONFIDENTIAL,
               confidential,
@@ -1283,6 +1284,22 @@ describe('Actions Notes Store', () => {
           });
       });
     });
+
+    describe('on user recoverable error', () => {
+      it('sends the error to Flash', () => {
+        const error = 'error';
+
+        jest
+          .spyOn(utils.gqClient, 'mutate')
+          .mockResolvedValue({ data: { issueSetConfidential: { errors: [error] } } });
+
+        return actions
+          .updateConfidentialityOnIssuable({ commit: () => {}, state, getters }, actionArgs)
+          .then(() => {
+            expect(Flash).toHaveBeenCalledWith(error, 'alert');
+          });
+      });
+    });
   });
 
   describe.each`