Payeezy Integration results in 403

Using the supplied example for Payeezy and creating a new account in Payeezy to use the `apiKey` and merchant `token` respectively results in the following response:

```json
{
"code": "403",
"message": "HMAC validation Failure"
}
```

Start by reproducing the supplied Payeezy example with the documented apiKey and merchant token, then inspect how the request is authenticated. Compare the generated HMAC inputs with Payeezy's requirements and confirm the result no longer returns the reported 403 HMAC validation failure.

Written by the indexing model from the issue text.