Provide rate limit http header to parse rate limits and create header values

[Spaier]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

I am creating a throttler for my own code, based on rate limit headers returned from several services and had to implement code that parses rate limits from headers which seems to be a standard https://datatracker.ietf.org/doc/draft-ietf-httpapi-ratelimit-headers/.
Headers that I use: X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset

Describe the solution you'd like

Since we already have AuthenticationHeaderValue and HttpRequestMessage.Headers.Authorization I think it might make sense to have RateLimitHeaderValue, RateLimitRemainingHeaderValue, RateLimitResetHeaderValue types defined somewhere in RateLimiting namespace and HttpRequestMessage.Headers.RateLimit extension that would return those values.

Additional context

No response

[martincostello]

Looks like this issue should be transferred to dotnet/runtime as it doesn't appear to be specific to ASP.NET Core as it relates to HttpClient.

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[MihaZupan]

Triage:

• There are many headers where we do expose strongly-typed values, and many where we don't.
• I don't know that this particular one would be more commonly needed, but I don't see an issue with exposing more in principle.
• If this is something that you care about, please upvote the top post so that we can gauge interest.
• In any case, we would wait for the spec to get finalized (currently in draft) - moving to Future.