Add priority field to queue (#705)
* feat: 🎸 inherit force=True in upsert_job
* feat: 🎸 add field "priority" to the jobs
Only two values are allowed: normal and low. We don't use an int to make
it easier for the moment.
* style: 💄 fix style
* fix: 🐛 test the creation of priority, not force
thanks @AndreaFrancis
* feat: 🎸 update docker images
