try to statically set caddy to prevent cloudflare hash breaking

pkgs/caddy/package.nix

@@ -0,0 +1,15 @@
+# Caddy with Cloudflare DNS
+
+{
+  pkgs,
+  ...
+}:
+
+# Maintain a static version so that the plugin hash doesn't keep breaking
+(pkgs.caddy.override {
+  version = "2.10.2";
+}).withPlugins
+  {
+    plugins = [ "github.com/caddy-dns/cloudflare@v0.2.1" ];
+    hash = "sha256-AcWko5513hO8I0lvbCLqVbM1eWegAhoM0J0qXoWL/vI=";
+  }