Complete the user registration process after OTP verification.

Prerequisites:

• Must have initiated signup via /auth/signup (unless using dq-dev-platform)
• Must have received and validated OTP (unless using dq-dev-platform)

Process:

1. Validates the OTP (if not dq-dev-platform)
2. Creates user account with provided details
3. Generates client credentials (client_id and secret)
4. Sends credentials to user's email (if not dq-dev-platform)

Response:
Returns client credentials that should be stored securely.
The secret is only shown once and cannot be retrieved later.

Important: Store your credentials securely. The secret cannot be recovered if lost.