Blazor SSR APIs for accessing HttpContext without IHttpContextAccessor

Ideally we’d support things like:

[FromHttpContext] public HttpRequest Request { get; set; }
[FromHttpContext] public HttpResponse Response { get; set; }

This is useful for things like:

• Reading the HTTP method
• Reading and writing cookies
• Setting arbitrary response headers

[SteveSandersonMS]

I guess it uses the AsyncLocal trick because it’s registered as a singleton. TBH I don’t know why IHttpContextAccessor is registered as singleton and not scoped, but perhaps it’s for back compat reasons. We wouldn’t need to do the same here.

If anyone knows of reasons why we shouldn’t have HttpContext accessible through a scoped service, please say so!

[DamianEdwards]

I think consistency wins here so sticking with the longer form name until such time we decide to support terser names for all the parameter-source attributes.