NodaTime Structs as dictionary keys in System.Text.Json

[buvinghausen]

Jon I have gone digging it looks like they exposed two virtual functions on JsonConverter in ReadAsPropertyName and WriteAsPropertyName and it doesn't look like the STJ serialization package supports either.

I'm going to take a stab at supporting it and tests and will open a PR as we use LocalDate as a dictionary key and need the support

[jskeet]

Righto, sounds good.

[buvinghausen]

Righto, sounds good.

PR up no rush on release as I have just ported the code into our repository and I'm #back2good

[jskeet]

Thanks - will get to it when I can. I'm reasonably comfortable ditching the netcoreapp3.1 target now that it's been out of support for a while.

[buvinghausen]

Yeah everything below .NET 6 has been out of support for over a year plus if someone is still running on 3.1 or 5 they can still use the .netstandard + STJ nuget shim.

[jskeet]

This is fixed in #120, but not yet released. I'll try to get round to a release next weekend, but I'll want to check for anything else we might want to do first.

[jskeet]

This is now in version 1.2.0. Please shout if you run into any problems.

[buvinghausen]

Thanks Jon!