Description
With request rate limiting, a common paradigm is to provide X-RateLimit-Remaining, X-RateLimit-Reset and X-RateLimit-Limit HTTP headers as useful information to the client. See Github and Laravel. Also, the RateLimit Header RFC defines these.

Currently, the component allows us to easily add X-RateLimit-Remaining, X-RateLimit-Reset but not X-RateLimit-Limit:

$limit = $limiter->consume();

$response->headers->add([
    'X-RateLimit-Remaining' => $limit->getRemainingTokens(),
    'X-RateLimit-Reset' => $limit->getRetryAfter()->getTimestamp(),
    'X-RateLimit-Limit' => // ???
]);

An attempt was made in #38257 to add via Limit::getMetadata() but ultimately rejected. The problem is while with the FixedWindowLimiter, the Limit is a clear value, with the TokenBucketLimiter it is a little fuzzy what it should be (perhaps the burst size?). Even the RFC is a little vague on this.

I'd like to reopen the discussion on this. Ping @nicolas-grekas, @wouterj