Feat/hook plugin support

[dhutchison]

Building on top of #315, this adds support for hooks to be defined by external plugins. These plugins are loaded from modules defined by the using package metadata.

This implements #302.

Leaving this as draft while I write the docs & commit the example projects, but this functionally appears to work...

[shadycuz]

@dhutchison If you need more permissions or anything else in this repo please let me know, we can always have a video call etc.

[dhutchison]

@dhutchison If you need more permissions or anything else in this repo please let me know, we can always have a video call etc.

Hey @shadycuz, apologies for the delay - I'd seen this, got busy, then couldn't find it again. Hope you are all ready for a great festive break!

Yeah it would probably be good if we were both able to merge & release and had some communication channel outside of just issues. I'm in holiday mode so not committing to doing anything till January :)

I've not looked at this specific PR in months - last I left it I could get it to work if the plugin was packaged and installed with pip OR poetry, but couldn't get the same detection code to work with both setups (i.e. if the plugin was packaged with poetry and installed using pip, it wouldn't detect). I'll get back to it at some point but python packaging is something completely new to me (all my development in python has been single project). The fact that common bits can come in from libraries easy enough with some fixtures might be enough, but I'll get back to this at some point.

Merry Chirstmas when it comes!