Add currency to body of _createCreditCardToken

[ambareng]

In _createCreditCardToken I added the curency property as it was missing. Without it the tokenization process does not know which currency you are using.

I need to specify currency as 'PHP' as if it is 'IDR' which is the default, amount needs to be an integer instead of possibly a decimal for Philippine currency.

Thanks and feel free to ask me any questions or concerns you may have.

[reynaldipane]

hi @ambareng , thanks for raising this PR!
I think we can have better validation to add currency in this _createCreditCardToken method

instead of adding the field directly in the body, I think we need to validate it first, and if its okay that we can add the field to the body. Like this:

    if(tokenData.currency !== undefined && tokenData.currency !== '') {
        body.currency = tokenData.currency;
    }

[boazcstrike]

Looks better than the initial proposed change. Works on our local.

[ambareng]

Hi @reynaldipane. Sorry if this is super late but I already updated my code according to your comments.
It'd be great if you could approve this pull request as it'll look good on my resume having contributions to a good open source project such as Xendit.

Thanks!