See 2020 REST API schema proposal: https://wmde.github.io/wikibase-rest-api-proposal/#/items/get_entities_items__entity_id_

BDD
As an API user
GIVEN I want to retrieve data about the item
WHEN I make a GET request to /entities/items/{item_id}
THEN I receive 200 HTTP response from the API
AND response contains full serialization of the item following the specification
AND headers of the response include the headers as defined in the specification

Acceptance criteria:

• Given ID of an existing item the API returns 200 HTTP response with item data following the structure defined in https://wmde.github.io/wikibase-rest-api-proposal/#/items/get_entities_items__entity_id_, and headers providing data on latest revision

Not included in this story:

• Filtering data fields to be included in the response (_fields paramater): T302055
• Conditional 304 responses (If-Modified-Since and If-None-Match parameters): T302060
• Mediawiki user authentication
• 404 response given non existing/incorrect Item ID: T302065

Notes:

• an estimate assumes the boiler plate set up has been completed: T302268
• Estimate based on assumption MW REST API framework can be used and endpoints can be added to it