hydra: remove hydra as its being decommissioned

nix-infra is built back in general, so remove hydra as well.

config/hosts/hydra/configuration.nix

@@ -1,9 +0,0 @@
-{ ... }:
-
-{
-  networking = {
-    hostName = "hydra";
-  };
-
-  system.stateVersion = "24.05";
-}

config/hosts/hydra/default.nix

@@ -1,11 +0,0 @@
-{ ... }:
-
-{
-  imports = [
-    ./configuration.nix
-    ./hydra.nix
-    ./networking.nix
-    ./nginx.nix
-    ./nix.nix
-  ];
-}

config/hosts/hydra/hydra.nix

@@ -1,15 +0,0 @@
-{ ... }:
-
-{
-  services.hydra = {
-    enable = true;
-    listenHost = "localhost";
-    port = 3000;
-    hydraURL = "https://hydra.hamburg.ccc.de/";
-    # E-Mail configuration requires some work/investigation still.
-    notificationSender = "no-reply@hydra.hamburg.ccc.de";
-    useSubstitutes = true;
-    minimumDiskFree = 8;
-    minimumDiskFreeEvaluator = 2;
-  };
-}

config/hosts/hydra/networking.nix

@@ -1,22 +0,0 @@
-{ ... }:
-
-{
-  networking = {
-    interfaces.net0 = {
-      ipv4.addresses = [
-        {
-          address = "172.31.17.163";
-          prefixLength = 25;
-        }
-      ];
-    };
-    defaultGateway = "172.31.17.129";
-    nameservers = [ "212.12.50.158" "192.76.134.90" ];
-    search = [ "hamburg.ccc.de" ];
-  };
-
-  systemd.network.links."10-net0" = {
-    matchConfig.MACAddress = "BC:24:11:45:7C:D6";
-    linkConfig.Name = "net0";
-  };
-}

config/hosts/hydra/nginx.nix

@@ -1,58 +0,0 @@
-{ config, pkgs, ... }:
-
-let
-  domain = "hydra.hamburg.ccc.de";
-in
-{
-  services.nginx = {
-    enable = true;
-
-    virtualHosts = {
-      "acme-${domain}" = {
-        default = true;
-        enableACME = true;
-        serverName = "${domain}";
-
-        listen = [
-          {
-            addr = "0.0.0.0";
-            port = 31820;
-          }
-        ];
-      };
-
-      "${domain}" = {
-        default = true;
-        forceSSL = true;
-        useACMEHost = "${domain}";
-
-        listen = [
-          {
-            addr = "0.0.0.0";
-            port = 8443;
-            ssl = true;
-            proxyProtocol = true;
-          }
-        ];
-
-        locations."/" = {
-          proxyPass = "http://${config.services.hydra.listenHost}:${builtins.toString config.services.hydra.port}";
-        };
-
-        extraConfig = ''
-          # Make use of the ngx_http_realip_module to set the $remote_addr and
-          # $remote_port to the client address and client port, when using proxy
-          # protocol.
-          # First set our proxy protocol proxy as trusted.
-          set_real_ip_from 172.31.17.140;
-          # Then tell the realip_module to get the addreses from the proxy protocol
-          # header.
-          real_ip_header proxy_protocol;
-        '';
-      };
-    };
-  };
-
-  networking.firewall.allowedTCPPorts = [ 8443 31820 ];
-  networking.firewall.allowedUDPPorts = [ 8443 ];
-}

config/hosts/hydra/nix.nix

@@ -1,10 +0,0 @@
-{ ... }:
-
-{
-  # Allow Hydra to fetch flake inputs.
-  nix.settings.allowed-uris = [
-    "github:"
-    "https://github.com/"
-    "https://git.hamburg.ccc.de/"
-  ];
-}