Request with unsafe method does not invalidate cache

[rhysemmerson]

Expected behaviour

When making a request with an unsafe method, all keys for that url should be invalidated.

GET /users      # MISS result stored in cache
POST /users    
GET /users     # MISS 

Actual Behaviour

Only the key for the unsafe method is invalidated.

GET /users      # MISS result stored in cache
POST /users  
GET /users     # HIT 

Potential solutions

One obvious solve would be to not use the request method in cache key, this wouldn't allow caching multiple methods though.

Alternatively the middleware could modify the request based on a configured set of methods and invalidate those methods.

private function invalidateCache(RequestInterface $request, ResponseInterface $response)
{
    $this->cacheStorage->delete($request);

    foreach ($this->invalidateMethods as $method) {
        $this->cacheStorage->delete($request->withMethod($method));
    }

    return $response->withHeader(self::HEADER_INVALIDATION, true);
}

[Kevinrob]

This is a good point! Do you want to make a PR for this? Link to the RFC about this: https://datatracker.ietf.org/doc/html/rfc7234#section-4.4