Spec/design document for competition admin form

[dunkOnIT]

We need an update to provide for series/twin competitions.

This will include:

• backend data model and logic (eg, for excluding competitors who have registered in a previous event in the series)
• React frontend, ideally using a step-by-step process instead of one long form.

A design document needs to be put together to describe this - Google Drive should suffice for storing it, with summaries which can be posted in the relevant child issues.

I am happy to assist with drawing up the spec, but would obviously require architectural and design guidance - @gregorbg perhaps a videocall at somepoint to talk the details of that? Shout if there's anyone else who should be included in that, given that it sounds like a non-trivial update and design process, with very invested stakeholders (both WCA team members, and those in the broader community).

We'll need a clear set of initial requirements, and someone who can "sign off" on those, as well as advise on whether implementation is on the right track assuming we follow an Agile methodology for this - which I would strongly advocate for.

[dunkOnIT]

Prematurely created - we can attend to matters like these as they become strategic priorities. Until they do, we aren't going to execute on them anyway, so issues like these are just clutter.