feat: add customizable caddy package (with plugin support)

pkgs/caddy.nix

@@ -0,0 +1,49 @@
+final: prev: let
+  inherit
+    (final.lib)
+    escapeShellArg
+    concatMapStrings
+    flatten
+    flip
+    ;
+
+  make-custom-caddy = {
+    plugins,
+    vendorHash,
+  }: let
+    caddyPatchMain =
+      flip concatMapStrings plugins
+      ({name, ...}: "sed -i '/plug in Caddy modules here/a \\\\t_ \"${name}\"' cmd/caddy/main.go\n");
+    caddyPatchGoGet =
+      flip concatMapStrings plugins
+      ({
+        name,
+        version,
+      }: "go get ${escapeShellArg name}@${escapeShellArg version}\n");
+  in
+    prev.caddy.override {
+      buildGoModule = args:
+        prev.buildGoModule (args
+          // {
+            inherit vendorHash;
+            passthru.plugins = plugins;
+
+            overrideModAttrs = _: {
+              preBuild = caddyPatchGoGet;
+              postInstall = "cp go.mod go.sum $out/";
+            };
+
+            postPatch = caddyPatchMain;
+            postConfigure = "cp vendor/go.mod vendor/go.sum .";
+          });
+    };
+in {
+  # Example usage:
+  # caddy.withPackages {
+  #   plugins = [
+  #     { name = "github.com/greenpau/caddy-security"; version = "v1.1.18"; }
+  #   ];
+  #   vendorHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
+  # }
+  caddy = prev.caddy.overrideAttrs (_: {passthru.withPackages = make-custom-caddy;});
+}

pkgs/default.nix

@@ -0,0 +1,3 @@
+[
+  (import ./caddy.nix)
+]