[feature request] return cache_metadata when creating the cache

[nschloe]

When creating a cache, one get the following info in the .extensions:

{
  'http_version': b'HTTP/1.1',
  'reason_phrase': b'OK',
  'network_stream': <httpcore._backends.sync.SyncStream object at 0x774d40e00050>,
  'from_cache': False,
  'revalidated': False
}

When fetching from cache, one gets

{
  'http_version': b'HTTP/1.1',
  'reason_phrase': b'OK',
  'from_cache': True,
  'cache_metadata': {
    'cache_key': '2b0e0bfa0bf634fbd3b40cad50e7e705',
    'created_at': datetime.datetime(2025, 1, 17, 14, 31, 18),
    'number_of_uses': 1
  },
 'revalidated': False
}

I need cache_metadata straight after creating the cache.