note: minor updates shoudl not container any db model changes
so we could choose to do a blue/green update if we wanted too to keep the control plan active or we can take a short downtime by scaling the stateful set to 0, updating the image and scaling back out.

we could also look at using the RollingUpdate update-strategy for this
https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/#update-strategies

for major upgrades we cannot use the RollingUpdate stragy as we must scale in all instance of the old container before scaling out the new ones.

schema migrations (db sync) can always be done before the container are updated.

as is true for all nova updates/upgrades the compute nodes should be updated after the other services. this is less important for a minor updated as in theory it is not required as rpc changes should never happen in a minor update however its still good practice to do them at the same time or after the other services.

this epic should span the end-to-end minor update process including the computes(libvirt and ironic).