Add error logging for a missing Authorization header during the minimal permission check

[bartizan]

If the Authorization header is missing in a request, the logs should show the error message "No Authorization header found" instead of "No scopes found in the token".
Applies to:

• ApiCenterMinimalPermissionsPlugin
• MinimalPermissionsGuidancePlugin
• MinimalPermissionsPlugin

[waldekmastykarz]

Good suggestion. That will be clearer. Thanks for the PR!