WIP: Date & time generators

[Qqwy]

Implementation of #129

• Date generator
  • Tests
• Time generator
  • Tests
• DateTime generator
  • Tests
• NaiveDateTime generator
  • Tests

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So far a generator function has added to create Date structs, including the accompanying tests.

The implementation for Time, DateTime and NaiveDateTime will be similar, except that their unit of offset will be fractions of milliseconds (rather than days), and of course the Date.Range-related code does not apply.

Since their implementation will be very similar, this seemed like a good moment to give you the opportunity to provide initial feedback on the code.

Happy holidays! 🎆

[Qqwy]

@whatyouhide Just a gentle reminder in case the notification of this PR slipped through the cracks.

Of course, take your time, and happy new-year's holidays! 😊

[whatyouhide]

I like where this is going. Is there any way we can use Date.add/2 (and eventually DateTime.add/3 and friends) here instead of converting between days and dates?

[Qqwy]

I like where this is going. Is there any way we can use Date.add/2 (and eventually DateTime.add/3 and friends) here instead of converting between days and dates?

I think this should be possible, at least for most of the cases. 👍