Better documentation of interaction between priority 0 and container state
current comment at https://doc.arvados.org/main/api/methods/container_requests.html is
Clients are expected to submit container requests with zero priority in order to preview the container that will be used to satisfy it. Priority can be null if and only if state!=“Committed”. See below for more details .
Priority 0 means no container should run on behalf of this request, and containers already running will be terminated (setting container priority to 0 is the cancel operation.)
Priority 1 is the lowest priority.
Priority 1000 is the highest priority.
Let's add a diagram showing the possible states and state changes.