Send rate limit headers when request is successful

[cristipufu]

Custom middleware

public interface IRateLimiterPolicy<TPartitionKey>
{
    Func<OnRejectedContext, CancellationToken, ValueTask>? OnRejected { get; }
+   Func<OnAcquiredContext, CancellationToken, ValueTask>? OnAcquired { get; }
}

public sealed class RateLimiterOptions
{
    public Func<OnRejectedContext, CancellationToken, ValueTask>? OnRejected { get; set; }
+    public Func<OnAcquiredContext, CancellationToken, ValueTask>? OnAcquired { get; set; }
}

dotnet/aspnetcore#44140

[hacst]

The API proposal for the feature request on the .NET side for this is in dotnet/aspnetcore#45658 and seems to be going into another direction.

There's a IRateLimiterStatisticsFeature portion which is actually intended to provide info for rate limit headers but it seems the discussion got bogged down on the specifics of that. TBO I am unsure whether it can even be made to work as well as the lease metadata approach for most of the limiters here. I think the thing that might be available the quickest is the part of the proposal that introduces a IRateLimiterLeaseFeature. That would make the lease available from middleware solving this issue here.

Lets see if they are up for my proposal to advance the IRateLimiterLeaseFeature independently.