Values:
DEFAULT (0):
Certificates with default scope are served
from core Google data centers. If unsure, choose
this option.
EDGE_CACHE (1):
Certificates with scope EDGE_CACHE are special-purposed
certificates, served from Edge Points of Presence. See
https://cloud.google.com/vpc/docs/edge-locations.
ALL_REGIONS (2):
Certificates with ALL_REGIONS scope are served from all
Google Cloud regions. See
https://cloud.google.com/compute/docs/regions-zones.