In the initial setup, entering an UNIX socket for the database host returns error

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Is your feature request related to a problem? Please describe.
I tried to use an existing unix- socket (filename) for Database-Host in setup, which usually can be taken as hostname. It returned an error saying the hostname cannot be resolved.

Describe the solution you'd like
i'd like to have that working with giving full filenames as usual.

Describe alternatives you've considered
It is already possible to use a format localhost:filename, which didn't seem to be self explaining to me as this is not a common annotation and is not mentioned anywhere.

Additional context
i already made it work and try to deliver a small push. have fun

Start at the initial setup flow where the database host is validated and compare handling of a full Unix-socket filename with the existing localhost:filename form. Done means a full socket filename is accepted as the database host without a hostname-resolution error, while the existing form continues to work.