[csharp] Duration format property support

[balassit]

Add support for duration property to be applied to format.
Currently only configured/built for c#. Need to determine path forward to implement further.

@wing328

Related to #14305

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[balassit]

@devhl-labs can you approve?

[devhl-labs]

I cant maybe @wing328

[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[balassit]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

Thanks. I think I have now fixed it and rebased all my commits down to one + the sync to merge it from master

[balassit]

@wing328 is this ready to go in now?

[wing328]

some builds failed. can you please take a look when you've time?

[balassit]

@devhl-labs can you help check the generichost failure? I have updated the JsonConverter.mustache, but not sure how to get it to now generate the updates needed to emit as JsonSerializer.Deserialize<Timespan>

[devhl-labs]

Looks like it will need a JsonConverter<TimeSpan> class. Feel free to exclude generichost from this change for now if you like.