IMPORTANT: Call from the back-end.

Once a user has taken custody of their Mintable Wallet, this permanently removes the private key from our systems. To ensure the user has indeed received and stored their private key, we require you to send us a hash of the last 8 characters of the key itself: once we have checked it against the actual key and, if the match is successful, we delete the key. The hash function used here is SHA-256 (please see this example).

This endpoint should always be called from your backend to prevent any potential spamming or exposing your private API key.