Improve error handling when deploying with basic auth

[philippfromme]

Describe the bug

As a follow-up to #4269 we should investigate whether we can improve the error handling when using basic auth to indicate to the user that the username or password is wrong.

Steps to reproduce

1. Deploy with basic auth enabled
2. Use wrong username or password
3. Generic error without indication that username or password wrong

Expected behavior

Indication that username or password wrong

Environment

• Camunda Modeler Version: 5.23

Additional context

#4269