Migrate to flakes

.gitignore

@@ -9,3 +9,4 @@ cover/
 apps/**/cover/
 priv/plts/
 doc/
+.direnv/

flake.nix

@@ -0,0 +1,32 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/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; };
+
+          # `sha256` can be programmatically obtained via running the following:
+          # `nix-prefetch-url --unpack https://github.com/elixir-lang/elixir/archive/v${version}.tar.gz`
+          elixir_1_15_7 = (pkgs.beam.packagesWith pkgs.erlangR26).elixir_1_15.override {
+            version = "1.15.7";
+            sha256 = "0yfp16fm8v0796f1rf1m2r0m2nmgj3qr7478483yp1x5rk4xjrz8";
+          };
+        in
+        with pkgs; {
+          devShells.default = mkShell {
+            buildInputs = [ elixir_1_15_7 inotify-tools docker-compose ];
+            env = {
+              POSTGRES_PORT="5432";
+              POSTGRES_USER = "postgres";
+              POSTGRES_PASSWORD = "postgres";
+              POSTGRES_DB = "endo_repo";
+            };
+          };
+        }
+    );
+}