Add Basic Auth for Apps

[mms-gianni]

Description

Apps should have a simple way to add Basic authentication.

Possible solution

"Advanced App Configuration" should get a new bar, to enable basic auth and manage users. 0-5 users are handled in a similar way as ENV vars are.

Alternatives

No response

Additional information

As for now, this feature is limited to NginX controllers. This should be stated in the docs and the app.