Add flake for composer v1

Still needed for a single legacy project.
Copied content from nixpkgs composer file and adopted for flake and v1.

flakes/projects/web/composer/flake.nix

@@ -0,0 +1,50 @@
+{
+  description = "Composer v1 for single legacy project.";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-21.11";
+    phps.url = "github:fossar/nix-phps/master";
+  };
+
+  outputs = {
+    self,
+    nixpkgs,
+    phps
+  }: {
+    defaultPackage.x86_64-linux =
+    let
+      pkgs = import nixpkgs { system = "x86_64-linux"; };
+      php = phps.packages.x86_64-linux.php73;
+      version = "1.10.25";
+    in pkgs.stdenv.mkDerivation {
+      pname = "composer";
+      inherit version;
+
+      src = pkgs.fetchurl {
+        url = "https://getcomposer.org/download/${version}/composer.phar";
+        sha256 = "sha256-awib2LeLAMPBXXsTNT+8vfFqP1JIIDyaPnbxOUjy3pI=";
+      };
+
+      dontUnpack = true;
+
+      nativeBuildInputs = [ pkgs.makeWrapper ];
+
+      installPhase = ''
+        runHook preInstall
+        mkdir -p $out/bin
+        install -D $src $out/libexec/composer/composer.phar
+        makeWrapper ${php}/bin/php $out/bin/composer \
+        --add-flags "$out/libexec/composer/composer.phar" \
+        --prefix PATH : ${pkgs.lib.makeBinPath [ pkgs.unzip ]}
+        runHook postInstall
+      '';
+
+      meta = with pkgs.lib; {
+        description = "Dependency Manager for PHP";
+        license = licenses.mit;
+        homepage = "https://getcomposer.org/";
+        changelog = "https://github.com/composer/composer/releases/tag/${version}";
+      };
+    };
+  };
+}