NotesE2ETests: Ensure posting the same note alias twice fails

Signed-off-by: Philip Molares <philip.molares@udo.edu>

test/public-api/notes.e2e-spec.ts

@@ -114,6 +114,15 @@ describe('Notes', () => {
         ),
       ).toEqual(content);
     });
+
+    it('fails with a existing alias', async () => {
+      await request(app.getHttpServer())
+        .post('/notes/test2')
+        .set('Content-Type', 'text/markdown')
+        .send(content)
+        .expect('Content-Type', /json/)
+        .expect(400);
+    });
   });
 
   describe('DELETE /notes/{note}', () => {