common: add module to disable RSA ssh hostkeys

Signed-off-by: Xe <me@christine.website>

common/default.nix

@@ -1,5 +1,5 @@
 { config, lib, pkgs, ... }: {
-  imports = [ ./users ./microcode.nix ];
+  imports = [ ./users ./microcode.nix ./no-rsa-ssh-hostkey.nix ];
 
   boot.cleanTmpDir = true;
   boot.kernelModules = [ "wireguard" ];

common/no-rsa-ssh-hostkey.nix

@@ -0,0 +1,6 @@
+{
+  services.openssh.hostKeys = [{
+    path = "/etc/ssh/ssh_host_ed25519_key";
+    type = "ed25519";
+  }];
+}