Add Event subclasses about auraxium

[leonhard-s]

(Continuing here to keep it with the issue itself)

@LordFlashmeow Feel free to take this one, it has been bugging me for a while too. I originally pushed this back because I was already working on moving to pydantic for the rest of the object model at the time and wanted to figure that out first.

Here are some thoughts I've written down for myself, for inspiration:

• events.py is already quite cluttered; the subclasses should therefore be part of the models sub module, same as the other object model data classes.
• This means that Event must inherit from pydantic.BaseModel (or Ps2Data, that way we also keep the immutability), with all other events inheriting from it
• These sub classes should have a type class attribute that points back to its enum equivalent (I want to keep the enums around for simplicity)
• Reimporting the sub classes into the events module is fine imo
• Should Trigger and related classes be extended to accept Event sub classes in place of EventType enums?

When implementing the MetagameEvent sub class, be wary of the zone_id field; it does not actually get sent with payloads anymore.
We can handle this in two ways: Either we don't include it at all and instead add a zone_id property that returns the appropriate value as per the reference in the Wiki, or we make it an optional field that defaults to -1, then add a pydantic validator that performs the same lookup and replacement if the value hasn't been changed. This also allows new alerts to just work in case the field ever gets fixed.

So yeah - if you want to help with this one, I'd appreciate it 👍

[leonhard-s]

Gonna try my hand at implementing the above; I don't want to have to write the event handler docs twice. :D

[leonhard-s]

Added in a24a7f0

[LordFlashmeow]

Nice, that's simpler than what I did. I'll make a draft pr so you can see what I was thinking.