update workflow for dev environment slightly

This changes the recommended venv manager to be uv in addition to
configuring a nix development shell.

.envrc

@@ -0,0 +1,3 @@
+use flake
+layout uv
+uv pip install --editable '.[django,djangorestframework]' -r requirements.dev.txt

.gitignore

@@ -1,4 +1,5 @@
 .idea
+.direnv
 venv
 dist
 docs/_build

DEVELOPMENT.md

@@ -20,15 +20,29 @@ py_simple_openid_connect/
    └ <others>                 (pytest based test suit)
 ```
 
-## How to set up the project
+## How to set up a dev environment
+
+### With nix
+
+If you use nix, this project provides a `flake.nix` file that defines a development shell with all dependencies installed.
+It can be entered by typing `nix develop`.
+Additionally, a [nix-direnv](https://github.com/nix-community/nix-direnv) configuration file is also present which also sets up a python environment suitable for development.
+
+### Manually
+
+Ensure you have the following system dependencies installed:
+- `python~=3.9`
+- a python virtual environment manager. This document assumes [uv](https://github.com/astral-sh/uv).
+
+Afterwards, follow the below commands to set up your development environment:
 
 ```shell
 # create a virtual python environment
-virtualenv venv
-# activate it
-source ./venv/bin/activate
-# install this project into the venv + dev dependencies
-pip install -e .[django,djangorestframework] -r requirements.dev.txt
+uv venv
+# install this project + its dev dependencies into the virtual environment
+uv pip install -e .[django,djangorestframework] -r requirements.dev.txt
+# activate the venv python interpreter for use (use the correct activation script for your shell though)
+source .venv/bin/activate
 ```
 
 ## How to run the Tests

flake.nix

@@ -0,0 +1,29 @@
+{
+  description = "Simple and opinionated OpenID-Connect relying party and resource server python library";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs =
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+    }:
+    flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = import nixpkgs { inherit system; };
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          packages = with pkgs; [
+            python312
+            uv
+          ];
+        };
+      }
+    );
+}