nixos/maddy: Add listeners option

[onny]

Motivation for this change

Support configuring listening addresses and port configuration for Imap, Submission and Smtp.
Configuration interface will look like this:

services.maddy = {
  enable = true;
  openFirewall = true;
  tls = {
    loader = "file";
    certificates = [{
      keyPath = "/tmp/key.pem";
      certPath = "/tmp/cert.pem";
    }];
  };
  ensureAccounts = [ "postmaster@localhost" ];
  ensureCredentials = {
    # Do not use this in production. This will make passwords world-readable
    # in the Nix store
    "postmaster@localhost".passwordFile = "${pkgs.writeText "postmaster" "test"}";
  };
  listeners = [
    {
      type = "imap";
      bind_addresses = [
        {
          tls = true;
          port = 993;
          address = "0.0.0.0";
        };
        {
          port = 143;
          address = "0.0.0.0";
        };
      ];
      extraConfig = ''
        auth &local_authdb
        storage &local_mailboxes
      '';
    };
  ];
};

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.05 Release Notes (or backporting 21.11 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

[McSinyx]

This is mentioned on nixos.wiki; should I wait for it or write TLS configuration by hand?

[onny]

This is mentioned on nixos.wiki; should I wait for it or write TLS configuration by hand?

I'm looking forward to further enhance this but it's difficult. I'm using this on my server but no guarantee yet it's working as expected.

[samip5]

How come this is still a draft?

[onny]

this is a difficult change, haven't managed to finish it yet :(