This commit add the functionnality to recreate the DEK based upon the
informations known by the submitter, even if the donor has removed his
DEK from the database. This DEK is only stored in the session of the
submitter, and is deleted once logged out.

This patch implements the check of the ownership of the case by the
connected submitter account. If the user dont have access to the
particular submission, a 403 will be returned. This function is cached
for 15 minutes in the Redis cache.