Allow value converters (JsonConverter<T>) to handle dictionary keys

[layomia]

This is a placeholder issue to expose the internal JsonSerializer mechanism for supporting non-string primitives as dictionary keys. This will allow custom (user-provided) converters to handle them. This involves making these two virtual methods public:

runtime/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonConverterOfT.cs

Lines 542 to 546 in cbc6aa6

	internal virtual T ReadWithQuotes(ref Utf8JsonReader reader)
	=> throw new InvalidOperationException();
	internal virtual void WriteWithQuotes(Utf8JsonWriter writer, [DisallowNull] T value, JsonSerializerOptions options, ref WriteStack state)
	=> throw new InvalidOperationException();

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Issue Details

---

This is a placeholder issue to expose the internal JsonSerializer mechanism for supporting non-string primitives as dictionary keys. This will allow custom (user-provided) converters to handle them. This involves making these two virtual methods public:

https://github.com/dotnet/runtime/blob/main/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonConverterOfT.cs#L542-L546

Author:	layomia
Assignees:	layomia
Labels:	api-suggestion, area-System.Text.Json
Milestone:	6.0.0

[jozkee]

Duplicate of #46520?

[layomia]

Yes, thanks @jozkee.