fix: postgres docker-compose startup

[Ekwav]

For getting started I expected to be able to use docker-compose -f docker-compose-postgres.yml up to start up a basic instance to test against and play around with.
This are the minimum changes I needed to accomplish this.
I am not sure what a good default namespace would be but without one the docker container crashes.

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
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  the changes.

Further Comments

[hperl]

Thanks for your PR, LGTM! 🎉

I think you are just one make format away from a green PR :)

[Ekwav]

Well I executed make format and now two checks fail 😅
I am not sure how to fix them :/