# Register or Check User Existence

Attempts to register a new user with the provided email. If the user already exists, it returns a 200 OK. If the user is successfully created, it returns a 201 Created. Both responses return the user's email.

Endpoint: POST /auth/signup
Version: 1.1.0
Security: m2m_oauth

## Request fields (application/json):

  - `email` (string, required)
    The email address for the user signup attempt.
    Example: "user@company.com"

  - `client_id` (string, required)
    The OAuth client_id of the company initiating the request.
    Example: "aBcDeFgHiJkLmNoPqRsT"

## Response 200 fields (application/json):

  - `email` (string, required)
    The email address associated with the signup status.
    Example: "user@company.com"

## Response 201 fields (application/json):

  - `email` (string, required)
    The email address associated with the signup status.
    Example: "user@company.com"

## Response 400 fields (application/json):

  - `code` (string, required)
    An application-specific error code string.
    Example: "INVALID_OTP"

  - `message` (string, required)
    A human-readable explanation specific to this occurrence of the problem.
    Example: "The OTP provided is invalid or has expired."

## Response 500 fields (application/json):

  - `code` (string, required)
    An application-specific error code string.
    Example: "INVALID_OTP"

  - `message` (string, required)
    A human-readable explanation specific to this occurrence of the problem.
    Example: "The OTP provided is invalid or has expired."