ExtractQueryLimitsContext gets the embedded limits from the context.

ExtractQueryLimitsHTTP retrieves the query limit policy from the HTTP header and returns it.

InjectQueryLimitsContext returns a derived context containing the provided query limits.

InjectQueryLimitsHTTP adds the query limits to the request headers.

NewQueryLimitsMiddleware creates a middleware that extracts the query limits policy from the HTTP header and injects it into the context of the request.

WrapTripperware wraps the existing tripperware to make sure the query limit policy headers are propagated.

NOTE: we use custom `model.Duration` instead of standard `time.Duration` because, to support user-friendly duration format (e.g: "1h30m45s") in JSON value.