DS_MERCHANT_PAYMETHODS parameter

[reimago]

Hi. It would be very useful if you could include the parameter "DS_MERCHANT_PAYMETHODS" in the payment parameters.

With this parameter you can indicate the possible payment methods.

C: Credit card only (will show only the form for credit card information)
A: Payment by Transfer (only if you have this payment method active)
D: Domiciliation (only if you have this payment method active)
T: Credit card + iupay (will show the form of the credit card and also the button iupay)

Thank you.

[shakaran]

@reimago z for bizum according to https://pagosonline.redsys.es/bizum.html

[brickpop]

Would you like to submit a PR for this?