Flawed logic in resource access token create service class when generating email

When working on Create resource access token with email contain... (!112548 - merged) I have noticed that this part of the CreateService contains flawed logic.

It checks if any User has the email as passed assigned. It doesn't check for secondary emails. That was causing a bug described here: #383216 (closed).

As we now are adding random string as a part of the email, chance of running into that bug again is minimal. However, we could improve that logic.