Cryptain for ClientExec
1. Upload the "plugins" folder into your ClientExec root (it adds plugins/gateways/cryptain).
2. Settings → Plugins → Gateways → Cryptain: enter your Cryptain URL, public key, secret key and webhook secret, then enable it.
3. In Cryptain (Dashboard → Stores → your store) set the Webhook URL to
   https://YOUR-CLIENTEXEC/plugins/gateways/cryptain/callback.php
Invoices are marked paid automatically when the crypto payment is confirmed.
