Add Uri StringSyntaxAttribute syntaxes

[blouflashdb]

Add Uri StringSyntaxAttribute syntaxes

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Description

Adds uri StringSyntaxAttribute syntaxes to all public APIs where an uri is expected.

Closes Uri Task in #44535

[ghost]

Thanks for your PR, @blouflashdb. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[blouflashdb]

Well somehow I can't use it in HubConnectionBuilderHttpExtensions.cs for some reason.
Check failure on line 26 in src/SignalR/clients/csharp/Client/src/HubConnectionBuilderHttpExtensions.cs

Azure Pipelines
/ aspnetcore-ci (Build Build: Linux ARM)
src/SignalR/clients/csharp/Client/src/HubConnectionBuilderHttpExtensions.cs#L26
src/SignalR/clients/csharp/Client/src/HubConnectionBuilderHttpExtensions.cs(26,131): error CS0122: (NETCORE_ENGINEERING_TELEMETRY=Build) 'StringSyntaxAttribute' is inaccessible due to its protection level

[JamesNK]

The SignalR client also targets .NET Framework, which doesn't have that attribute.

To work around this:

1. Copy the attribute's source code from StringSyntaxAttribute.cs
2. Add an internal polyfill type in the Shared/CodeAnalysis directory - https://github.com/dotnet/aspnetcore/tree/1b53b22a866eb4bc58f2d5552db7f3ac08f1a952/src/Shared/CodeAnalysis. The trimming types already in that directory are a good example of this technique.
3. Finally, add a link to the shared source file from the SignalR client project.

It doesn't matter that the attribute is internal and in a different assembly. As long as the type name and namespace match, tooling and other apps can use it.

[blouflashdb]

Thanks, I think I got it.

[JamesNK]

RelativeOrAbsolute would be the default assumption so there is no need to explicitly specify it.

Otherwise, LGTM