Add alter event processing to collector

alexandersluiter → closed merge request !42

This patch takes the original patch and applies it to the latest release (2.0.2)

There was something missing in the previous patch. Here is the working one

timohuisman → closed merge request !74

Not specifically sure the old module supported event level alteration, but it's a good idea and something I'm tagging to make sure we review / help push forward as part of that initiative.

A less invasive solution may be proposed in ✨ Allow to alter order item data for commerce events Needs review ; cross-linking here.

I didn't see this issue when I worked on mine. What I struggled with in my implementation was making the necessary context available to the event in a useful way. Many of the commerce plugins work in different ways, their context differs and the data they produce differs. My MR focuses on unifying that and having more specific events that work for many different events.