$ curl -i -X PUT http://localhost:8080/api/products/42 \
     -H 'Content-Type: application/json' -H 'If-Match: "4e47fa7e"' \
     -d '{"name":"Laptop Pro","price":1199}'

HTTP status: 200
Old ETag: "4e47fa7e"
New ETag: "0087226b" (rotated -- a stale If-Match sent after this point 412s)
Body: {"id":42,"name":"Laptop Pro","price":1199,"version":2}
