Add isBackOffice, isPayLater, getPaymentMode helpers to frontendpaymentformtrait
Created by: mattwire
This adds helper functions and properties to
get/SetPaymentMode() so we don't have to interact directly with the properties and do not have to specify them on each form.
Developed for #17508
Direct access to properties, they must be specified on each form.
frontendpaymentformtrait and the new methods.