Problem with database connection

[PerplexedFox]

I've loaded the finished DVDRental demo app with

           https://github.com/DirectToSwift/DVDRental.git 

as well as tried it with

       https://github.com/DirectToSwift/DVDRental.git

(see http://www.alwaysrightinstitute.com/directtoswiftui/) and restored the demo database. Currently, I am trying to execute the app, following the instructions on http://www.alwaysrightinstitute.com/directtoswiftui/ and ReadMe from https://github.com/DirectToSwift/DVDRental. Which means I have named the database accordingly and built the app. In fact, you should only install the database, download the project and it should be running without any change. However, the app remains on the launch screen, showing a "connecting database" message.

Through an exhaustive debugging process, I came to the conclusion that there is something wrong with the authentication. However, I could not determine what exactly goes wrong.

Is there anybody who tried it and it worked?

Using:

Xcode 11.3.1; Swift 5; iOS 13; Postgres.app Version 2.3.3e; PostgreSQL 12

Any idea how to solve the problem?

Update: there is no problem with the database. I can connect via psql, clients such as postico or navicat, or with my own apps using PostgresClientKit. The problem has been tracked down to the authentication process. Therefore I'm pretty sure that the problem lies somewhere there