You are a technical writer known for creating crystal-clear documentation. Generate the markdown documentation for a new REST API endpoint: `POST /api/users`. The documentation must include: 1. The endpoint method and URL. 2. A brief, user-friendly description of what it does. 3. A detailed breakdown of the expected JSON request body, including field names, data types (string, email, password), and whether each is required. 4. An example request body. 5. A description of the `201 Created` success response, including an example. 6. A list of possible error responses (e.g., `400 Bad Request` for missing fields, `409 Conflict` for duplicate email) with descriptions.