Initial refactor of PayPal core processor to stop using doDirectPayment/doTransferCheckout

[mattwire]

Overview

PayPal core payment processor is calling doDirectPayment and doTransferCheckout via parent doPayment() method. This PR re-implements doPayment() directly on the PayPal class and renames the doDirectPayment/doTransferCheckout methods to make it clear that they have no dependency on legacy core code.

Before

Relies on legacy core code to call legacy methods.

After

Self-contained code using standard doPayment() as entry-point.

Technical Details

This would allow for further refactoring/simplification in the future. It is now obvious that the methods are internal to PayPal.

Comments

[civibot]

(Standard links)

• If this is your first pull-request for CiviCRM, please browse CONTRIBUTING.md for information about the development and testing processes.
• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).

[mattwire]

Core doPayment() assumes that doTransferCheckout() returns but for PayPal it does not because CRM_Utils_System::redirect() is called at the end of the function.

[eileenmcnaughton]

I gave the code a quick skim & this makes sense - I haven't gone through more carefully/tested at this stage

[eileenmcnaughton]

@mattwire it's a looong time since we consolidated on doPayment but it used to be the case that doTransferCheckout & doDirectPayment were directly called. Until your PR yesterday we never actually put a deprecation notice in them!

I think I'd feel more comfortable is we added them back with a deprecation notice & a call to the renamed function just in case

[mattwire]

@eileenmcnaughton Ok that makes sense. I've added the legacy methods with deprecated warnings.

[eileenmcnaughton]

thanks @mattwire

[eileenmcnaughton]

OK - I've read through this a couple more times & I'm pretty comfortable that it is just moving the furniture and won't change (break) anything