Allows customers to configure tenant_id for GCIP instance per-app.
GCIP tenant ids that are linked to the IAP resource.
tenant_ids could be a string beginning with a number
character to indicate authenticating with GCIP tenant flow,
or in the format of \_ to indicate authenticating with GCIP
agent flow. If agent flow is used, tenant_ids should only
contain one single element, while for tenant flow,
tenant_ids can contain multiple elements.
Login page URI associated with the GCIP
tenants. Typically, all resources within the
same project share the same login page, though
it could be overridden at the sub resource