Add default.nix using cabal2nix

default.nix

+{ mkDerivation, base, bytestring, mtl, optparse-applicative
+, optparse-generic, servant, servant-server, shelly, stdenv, text
+, warp, zlib
+}:
+mkDerivation {
+  pname = "terraform-http-backend-pass";
+  version = "0.1.0.0";
+  src = ./.;
+  isLibrary = true;
+  isExecutable = true;
+  libraryHaskellDepends = [
+    base bytestring mtl optparse-applicative optparse-generic servant
+    servant-server shelly text warp
+  ];
+  librarySystemDepends = [ zlib ];
+  executableHaskellDepends = [ base ];
+  license = "unknown";
+  hydraPlatforms = stdenv.lib.platforms.none;
+}