Add additional options param

[pauline-koch]

Hello,

Thank you for this cool project. I added a param to the json_transaction that allows setting all parameters in the transaction request to the datatrans api. My use case is that I want to use different webhook endpoints during development/QA without creating multiple datatrans testaccounts. With this new option any json param can be sent to the /transactions endpoint.

Let me know if this works for you.

Best Regards