Server timestamps

In order to avoid race conditions, all timestamps manipulated by the server are not true HTTP date values, nor milliseconds EPOCH timestamps.

They are milliseconds EPOCH timestamps with the guarantee of a change per timestamp update. If two changes happen at the same millisecond, they will have two differents timestamps.

The ETag header with the last timestamp of the collection for a given user will be given on collection and record GET endpoints.

ETag: "1422375916186"

All timestamp of the app will be set in milliseconds.