upgrade from hip to massiv-io, move to nixpkgs unstable in the process

flake.nix

@@ -1,14 +1,12 @@
 {
   description = "srid/haskell-template: Nix template for Haskell projects";
   inputs = {
-    nixpkgs.url = "github:nixos/nixpkgs/nixos-23.05";
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
     systems.url = "github:nix-systems/default";
     flake-parts.url = "github:hercules-ci/flake-parts";
     haskell-flake.url = "github:srid/haskell-flake";
     treefmt-nix.url = "github:numtide/treefmt-nix";
     treefmt-nix.inputs.nixpkgs.follows = "nixpkgs";
-    hip.url = "github:lehins/hip";
-    hip.flake = false;
   };
 
   outputs = inputs:
@@ -30,28 +28,10 @@
           packages = {
             # Add source or Hackage overrides here
             # (Local packages are added automatically)
-            # https://github.com/lehins/hip.git
-            # hip.source = inputs.hip + "/hip";
           };
 
           # Add your package overrides here
           settings = {
-
-            /*
-            haskell-template = {
-              haddock = false;
-            };
-            aeson = {
-              check = false;
-            };
-            */
-            hip = {
-              jailbreak = true;
-              broken = false;
-              failOnAllWarnings = false;
-              check = false;
-              # extraBuildFlags = ["--ghc-option=-Wno-incomplete-uni-patterns"];
-            };
           };
 
           # Development shell configuration
@@ -75,12 +55,6 @@
 
           # We use fourmolu
           programs.ormolu.package = pkgs.haskellPackages.fourmolu;
-          settings.formatter.ormolu = {
-            options = [
-              "--ghc-opt"
-              "-XImportQualifiedPost"
-            ];
-          };
         };
 
         # Default package & app.