feat: initial users store

README.md

@@ -22,6 +22,22 @@ After you have installed all dependencies you can now run the app.
 Run `npm start` to start a local server.
 The port will be displayed to you as `http://0.0.0.0:3333` (or if you prefer IPv6, if you're using `express` server, then it's `http://[::1]:3333/`).
 
+## Initial users
+
+Adding a JSON file with the following layout will populate the users store when starting:
+
+```json
+{
+  "email@test.com": {
+    "given_name": "name",
+    "family_name": "family",
+    "user_id": "id"
+  }
+}
+```
+
+By default `./users.json` will be read but this can be overridden by setting the environment variable `USERS_FILE`.
+
 ## API Documentation
 
 ### `GET` /token/:username