feat: update nix flake

flake.nix

@@ -4,7 +4,7 @@
   inputs.nixpkgs.follows = "haskellNix/nixpkgs-unstable";
   inputs.flake-utils.url = "github:numtide/flake-utils";
   inputs.CHaP = {
-      url = "github:input-output-hk/cardano-haskell-packages?ref=repo";
+      url = "github:IntersectMBO/cardano-haskell-packages?ref=repo";
       flake = false;
     };
   outputs = { self, nixpkgs, flake-utils, haskellNix, CHaP }:
@@ -26,6 +26,41 @@
         };
 
         overlays = [ haskellNix.overlay
+          (final: prev: {
+            webkitgtk = final.webkitgtk_4_0;
+            libsodium = with final; stdenv.mkDerivation rec {
+              pname = "libsodium";
+
+              src = fetchGit {
+                url = "https://github.com/IntersectMBO/libsodium";
+                rev = version;
+              };
+              version = "dbb48cce5429cb6585c9034f002568964f1ce567";
+
+              nativeBuildInputs = [ autoreconfHook ];
+
+              configureFlags = [ "--enable-static" ]
+                # Fixes a compilation failure: "undefined reference to `__memcpy_chk'". Note
+                # that the more natural approach of adding "stackprotector" to
+                # `hardeningDisable` does not resolve the issue.
+                ++ lib.optional stdenv.hostPlatform.isMinGW "CFLAGS=-fno-stack-protector";
+
+              outputs = [ "out" "dev" ];
+              separateDebugInfo = stdenv.isLinux && stdenv.hostPlatform.libc != "musl";
+
+              enableParallelBuilding = true;
+
+              doCheck = true;
+
+              meta = with lib; {
+                description = "A modern and easy-to-use crypto library - VRF fork";
+                homepage = "http://doc.libsodium.org/";
+                license = licenses.isc;
+                maintainers = [ "tdammers" "nclarke" ];
+                platforms = platforms.all;
+              };
+            };
+          })
           (final: prev: {
             hixProject =
               final.haskell-nix.project' {
@@ -34,16 +69,18 @@
                 # This is used by `nix develop .` to open a shell for use with
                 # `cabal`, `hlint` and `haskell-language-server`
                 shell.tools = {
-                  cabal = {}  ;
+                  cabal = {};
                   hlint = {};
                   haskell-language-server = {};
                   # ghc-lib-parser doesnt compile with anything newer
                   fourmolu = "0.17.0.0";
                 };
                 # Non-Haskell shell tools go here
-                shell.buildInputs = with pkgs; [
+                shell.buildInputs = with final; [
                   nixpkgs-fmt
                 ];
+                # ???: Fix for `nix flake show --allow-import-from-derivation`
+                evalSystem = "x86_64-linux";
                 inputMap = { "https://chap.intersectmbo.org/" = CHaP; };
               };
           })
@@ -53,5 +90,16 @@
         flake = pkgs.hixProject.flake {};
       in flake // {
         legacyPackages = pkgs;
+        # Built by `nix build .`
+        packages.default = flake.packages."atlas-cardano:lib:atlas-cardano";
       });
+  # --- Flake Local Nix Configuration ----------------------------
+  nixConfig = {
+    # This sets the flake to use the IOG nix cache.
+    # Nix should ask for permission before using it,
+    # but remove it here if you do not want it to.
+    extra-substituters = ["https://cache.iog.io"];
+    extra-trusted-public-keys = ["hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ="];
+    allow-import-from-derivation = "true";
+  };
 }