Set X-Cache and X-Cache-Lookup headers for cache (#8794)

X-Cache sets cache status of HIT if object is
served from the disk cache, or MISS otherwise.
X-Cache-Lookup is set to HIT if object was found
in the cache even if not served (for e.g. if cache
 entry was invalidated by ETag verification)

cmd/object-api-datatypes.go

@@ -143,6 +143,11 @@ type ObjectInfo struct {
 	// Date and time at which the object is no longer able to be cached
 	Expires time.Time
 
+	// CacheStatus sets status of whether this is a cache hit/miss
+	CacheStatus CacheStatusType
+	// CacheLookupStatus sets whether a cacheable response is present in the cache
+	CacheLookupStatus CacheStatusType
+
 	// Specify object storage class
 	StorageClass string