API Documentation Generator

Act as a Technical Writer. Write documentation for this API endpoint.

Endpoint: POST /api/v1/users/register

Inputs:

• email (required, string)
• password (required, min 8 chars)
• referral_code (optional)

Responses:

• 201: Created.
• 400: Validation Error.
• 409: User already exists.

Output Format:

• Markdown.
• Include an example cURL request.
• Include a JSON example of a success response.