Extract cancelParticipant and cancelMembership functions in baseIPN

[mattwire]

Overview

This extracts the "business logic" ie. cancelParticipant() and cancelMembership() in baseIPN so we have a single functions that handles these functions instead of being duplicated across two functions cancelled() and failed().
Partial from #14397

Before

Code duplicated in two places.

After

Code only in one place.

Technical Details

This is a straight extraction, no functional changes should have been made.

Comments

@eileenmcnaughton @sluc23

[civibot]

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[eileenmcnaughton]

@mattwire this seems basically OK to me - I'm just wondering why you made the 2 new functions static (I like that they are private).

I'm Ok with this but we should add tests if we make any further changes / cleanup here. I'd also like to deprecate the failed & cancelled functions - we might be stuck with some behaviours for paypal but we should establish our preferred behaviour as an api & encourage other processors to use that.

[mattwire]

@eileenmcnaughton They don't need to be static - thanks for spotting - I've changed.

I don't think I'll be making further changes to the baseIPN class and agree that most stuff should be deprecated. Once this is merged the cancelParticipant() and cancelMembership() functions provide a single point that could be overridden in some way to change that logic per dev/core/issues#927

[eileenmcnaughton]

unrelated fail