Resolve `postgres` container reporting FATAL: role "root" does not exist

[devraj]

Describe the bug
The postgres container continually reports

labs-postgres       | 2023-04-24 23:20:09.585 UTC [463] FATAL:  role "root" does not exist

To Reproduce
Monitor the logs of the database container

Expected behavior
This exception should not be thrown. We should resolve this as part of the container configuration.

[devraj]

This is caused the healthcheck configuration

      test: [ "CMD-SHELL", "pg_isready", "-U", "${POSTGRES_USER}", "-d", "${POSTGRES_DB}" ]

I have found other repositories reporting the same issue and there are mixed reports of success.