A filter specifying what Service\ s to return. The filter
currently supports the following fields: :: -
identifier_case - app_engine.module_id -
cloud_endpoints.service - cluster_istio.location -
cluster_istio.cluster_name -
cluster_istio.service_namespace -
cluster_istio.service_nameidentifier_case refers to
which option in the identifier oneof is populated. For
example, the filter identifier_case = "CUSTOM" would match
all services with a value for the custom field. Valid
options are “CUSTOM”, “APP_ENGINE”, “CLOUD_ENDPOINTS”, and
“CLUSTER_ISTIO”.
If this field is not empty then it must contain the
nextPageToken value returned by a previous call to this
method. Using this field causes the method to return
additional results from the previous method call.