opensmtpd-filter-rspamd: init at 0.1.7

[Flakebi]

Motivation for this change

A filter to integrate rspamd with opensmtpd: https://github.com/poolpOrg/filter-rspamd

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[Ekleog]

This looks interesting, thank you! Do you think you could add a test based on nixos/tests/opensmtpd.nix (feel free to copy/paste it into another file, it should just be a matter of copy-pasting, adding the required configuration lines and adding a grep in the check-it-works script), so that it is easy to check that this package keeps working and being compatible with opensmtpd as time pass?

(And then add it to nixos/tests/all-tests.nix and to the passthru.tests attribute of the derivation you added so it gets automatically tested by our infrastructure)

(Just FYI, there was #122403 aiming at the same thing, but it looks like the author there doesn't want to commit to maintaining this package, so it would probably be better to merge your version :))

[Flakebi]

Thanks for the review, I added a test.

The last time I checked there was no other pr yet, seems like @wizeman and me ended up writing exactly the same code :)

[Ekleog]

Awesome, thank you!