services/postgresql: update to the latest upstream nixos module

[lf-]

I want a newish postgres config to work on my Mac.

This contains a little hack (putting the check-config derivation into
the start script as a comment) to deal with not having #356. Also,
it does not implement the stuff that requires a postStart script.

It's otherwise identical to the upstream module.

I changed the service to use utf8 always because the charset option got deleted in the upstream module. It seems to work and I can connect to it.

[olib963]

First of all, thanks for all the great work 😄 it's great to be able to use nix on all my machines. I just wanted to point out that post this PR I am now getting:

1. initdb: error: no data directory specified as I believe we've removed -D ${cfg.dataDir} from the initdb call, I think this should be a fairly easy fix either explicitly or by adding this into the initdbArgs by default which is my workaround, but wanted to check if there was a reason it was excluded?
2. Peer authentication failed for user "postgres" I believe this is due to the addition of authentication files, I've added a workaround locally by setting: authentication= ''local all postgres trust''; but I'm not sure the change is documented in any way. Given that we don't yet have the ability to ensureUsers perhaps we should add a documenting comment as I'm struggling to see how to setup a clean database.

Happy to open PRs if we are comfortable proceeding with either of the above.

@lf- did you manage to get a clean database setup using this configuration? Perhaps I did something wrong in my setup.

[lf-]

Yes I used it every day with this module so it definitely works. no recollection as to how the auth was set up, it was done 6 months ago, and i don't have the computer anymore.