fix: use redis cache interface instead of concreate object for urlcache init

// urlCacheStorageMiddleware provides a caching layer for URLFor calls using an in-memory LRU cache.

type urlCacheStorageMiddleware struct {

	driver.StorageDriver

	cache              *iredis.Cache

	cache              iredis.CacheInterface

	dryRun             bool

	minURLValidity     time.Duration

	defaultURLValidity time.Duration

	if v == nil {

		return nil, nil, fmt.Errorf("redis cache has either been not defined in container registry config or is not usable and it is required by urlcache middleware to work")

	}

	redisCache, ok := v.(*iredis.Cache)

	redisCache, ok := v.(iredis.CacheInterface)

	if !ok {

		return nil, nil, fmt.Errorf("redis cache passed to the middleware cannot be used as the type is wrong: %T", v) // this should not happen either

	}