The role of subnetwork. Currently, this field is only used when
purpose = REGIONAL_MANAGED_PROXY. The value can be set to ACTIVE or
BACKUP. An ACTIVE subnetwork is one that is currently being used for
Envoy-based load balancers in a region. A BACKUP subnetwork is one
that is ready to be promoted to ACTIVE or is currently draining.
This field can be updated with a patch request.
Values:
UNDEFINED_ROLE (0):
A value indicating that the enum field is not
set.
ACTIVE (314733318):
The ACTIVE subnet that is currently used.
BACKUP (341010882):
The BACKUP subnet that could be promoted to
ACTIVE.