As an application developer I only want to load the updated data from Wikibase instance, so I can update it in my app
See `If-None-Match` and `If-Modified-Since` parameters in https://wmde.github.io/wikibase-rest-api-proposal/#/items/get_entities_items__entity_id_
**BDD**
As an API user
GIVEN there is a newer version of item data than revision ID N
WHEN I make a GET request to /entities/items/{item_id}
AND I provide N as the revision ID in If-None-Match
THEN I receive 200 HTTP response from the API
AND response contains item data
As an API user
GIVEN The most recent version of an item is N
WHEN I make a GET request to /entities/items/{item_id}
AND I provide N as the revision ID in If-None-Match
THEN I receive 304 HTTP response from the API
AND response headers contain the item metadata as indicated in the proposal