Permanently close a user account so it can no longer be used
UserCategory OWNER and PAYER and for all types of Legal user (Business, Partnership, Organization, Soletrader).
When a User is closed (whether via this endpoint or by Mangopay):
UserStatus changes to CLOSED (and the USER_ACCOUNT_CLOSED webhook is sent)204 - No Content
400 - Wallets not empty
400 - User already closed