[csharp][generichost] Fix dateTimeOffset bug

[devhl-labs]

Fixes #23338

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---

Summary by cubic

Fixes incorrect date-time handling in the C# generichost client when useDateTimeOffset is enabled. Date-time fields now use DateTimeOffset for deserialization, resolving #23338 and preventing timezone loss and casting errors.

• Bug Fixes
  • Updated JsonConverter.mustache to deserialize date-time properties as DateTimeOffset when useDateTimeOffset is true.
  • Added bin/configs/csharp-generichost-latest-dateTimeOffset.yaml and generated sample at samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset.
  • Included the new sample in .github/workflows/samples-dotnet10.yaml to build and test in CI.

^{Written for commit 4f50766. Summary will update on new commits.}

[cubic-dev-ai]

5 issues found across 378 files

Note: This PR contains a large number of files. cubic only reviews up to 75 files per PR, so some files may not have been reviewed.

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/docs/models/NullableClass.md">

<violation number="1" location="samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/docs/models/NullableClass.md:10">
P2: Documentation lists optional value-type properties as non-nullable, but the generated model uses nullable types, so the docs are inaccurate and misleading about null handling.</violation>
</file>

<file name="samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/docs/apis/PetApi.md">

<violation number="1" location="samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/docs/apis/PetApi.md:286">
P2: Stream parameter type is rendered twice in API docs (`System.IO.Stream****System.IO.Stream`), producing malformed type text.</violation>
</file>

<file name="samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/docs/apis/FakeApi.md">

<violation number="1" location="samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/docs/apis/FakeApi.md:60">
P2: Docs list optional value-type parameters as non-nullable (`bool`, `decimal`, `int`, etc.) while also giving them `= null` defaults. This is not a valid C# signature and misleads users; optional value types should be nullable (`T?`) or use a non-null default.</violation>

<violation number="2" location="samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/docs/apis/FakeApi.md:451">
P2: Parameter type documentation is corrupted for binary stream (`System.IO.Stream` duplicated with broken markdown), reducing API doc correctness.</violation>

<violation number="3" location="samples/client/petstore/csharp/generichost/latest/UseDateTimeOffset/docs/apis/FakeApi.md:674">
P2: The documented C# method signature is invalid because it places a required parameter after optional parameters.</violation>
</file>

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