save_code_now: Add snasphot info in data returned by API endpoint
When sending a GET request to /api/1/origin/save/(visit_type)/url/(origin_url)/
endpoint, the SWHID of the resulting snapshot for a save request is now part of
the returned data along with the snapshot URL.
The snapshots associated to the save code now visits for a given origin are
retrieved on demand and then put in cache in the SaveOriginRequest
django
model.
Related to #4726 (closed)