Allows selecting how infrastructure upgrades should be
applied to the cluster or node pool.
Values:
MAINTENANCE_INTERVAL_UNSPECIFIED (0):
The maintenance interval is not explicitly
specified.
AS_NEEDED (1):
Nodes are eligible to receive infrastructure
and hypervisor updates as they become available.
This may result in more maintenance operations
(live migrations or terminations) for the node
than the PERIODIC option.
PERIODIC (2):
Nodes receive infrastructure and hypervisor updates on a
periodic basis, minimizing the number of maintenance
operations (live migrations or terminations) on an
individual VM. This may mean underlying VMs will take longer
to receive an update than if it was configured for
AS_NEEDED. Security updates will still be applied as soon as
they are available.