Finally switch to flakes.

nixos/services/openssh.nix

@@ -0,0 +1,21 @@
+{
+  # Enable SSH
+  services = {
+    openssh = {
+      enable = true;
+      settings = {
+        PermitRootLogin = "no";
+        PrintLastLog = "no";
+        PasswordAuthentication = false;
+      };
+    };
+
+    # Block nefarious SSH connections
+    fail2ban = {
+      enable = true;
+      maxretry = 5;
+      bantime = "5m";
+      ignoreIP = [ "10.0.0.0/24" ];
+    };
+  };
+}