Cookbook example showing custom calendar proof of concept (without custom calendar object)

[ptomato]

This is an example of how to approach implementing a custom calendar, after Temporal.Calendar objects are removed.

It's an implementation of a Nepali calendar (described by @kabaros in #2854 (comment)) based on the implementation linked in that comment, as well as the implementation that was based on.

I used inheritance in this example because in this case that's slightly less code to write, but inheritance also makes some operations legal that maybe shouldn't be. (Like, Temporal.PlainDateTime.from(nepaliPlainDate)) So it might be better to switch to composition.

I'd also like to write a similar example about Hijri dates with manual adjustment (described in #2854 (comment)) but it was easier to do the proof of concept with Nepali calendar first, since there was already an implementation to copy from. I'll be in contact with @khawarizmus about this.

Draft; needs some cleanup, and a cookbook page.

[kabaros]

thanks @ptomato - this is very helpful (and re-assuring).

[ptomato]

I found some time to clean this up and make a cookbook page for it. It's ready for review now.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.85%. Comparing base (87c74ec) to head (78179d8).
Report is 13 commits behind head on main.

Additional details and impacted files

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  Files          21       21           
  Lines        9969     9969           
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  Hits         9655     9655           
  Misses        268      268           
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[gibson042]

This is rather nice.

[ptomato]

@sffc Did you still want to review this? I'd like to get it done soon.

[sffc]

Praise: Very clear and well-commented!

I didn't verify the calendar arithmetic for correctness.

[ptomato]

Thanks for taking a look. I just implemented the calendar arithmetic that was in the other library that I credited, so I haven't done any research on correctness. I think that's OK for a cookbook example. Hopefully we will get feedback if it isn't accurate 😄