✅(demo) change email from user to user.test in demo

When we create a new user in the demo environment,
the email address will now follow the format
user.test@example.com instead of user@example.com.
"user" was only 4 characters long, it created failing
tests in the e2e suite.

src/frontend/apps/e2e/__tests__/app-impress/doc-member-create.spec.ts

@@ -15,7 +15,7 @@ test.describe('Document create member', () => {
   });
 
   test('it selects 2 users and 1 invitation', async ({ page, browserName }) => {
-    const inputFill = 'user ';
+    const inputFill = 'user.test';
     const responsePromise = page.waitForResponse(
       (response) =>
         response.url().includes(`/users/?q=${encodeURIComponent(inputFill)}`) &&