services: move .nix files into their own dirs

modules/services/ssh/module.nix

@@ -0,0 +1,20 @@
+{lib, ...}: let
+  inherit (lib.options) mkEnableOption;
+in {
+  options.modules.programs.ssh.enable = mkEnableOption "ssh";
+  config = {
+    # set the ssh socket globally. This alows all applications and shells to use
+    # the ssh-agent.
+    environment.sessionVariables.SSH_AUTH_SOCK = "/run/user/1000/ssh-agent";
+    programs.ssh.startAgent = true;
+
+    services.openssh = {
+      enable = true;
+      ports = [22];
+      settings = {
+        PasswordAuthentication = false;
+        PermitRootLogin = "no";
+      };
+    };
+  };
+}