The files under db_config/test were generated for the purpose of testing the SSL connection locally.
When mounting server.key as a volume to be used be Postgres, make sure that the file has the correct permissions.
This can be achieved by setting the Read/Write permissions for the owner only: chmod 600 server.key (reference).
Do not use these files in a live environment
Additionally, the self-signed certificate is a X509 certificate generated on March 1, 2024, with validity of 365 days.
The CN used was localhost.