[Metricbeat] Add GCP CloudSQL region filter (#32943)

* add cloudsql region filter

* add changelog entry

* fix comment for golangci-lint

* fix get filter for metric tests

* better AlignersMapToGCP comment

* revert to zone and add comment

* Revert "fix get filter for metric tests"

This reverts commit e3ea3b8.

* add cloudsql region label

* add regions filter

* fix changelog

* remove comment from metrics requester

CHANGELOG.next.asciidoc

@@ -88,6 +88,7 @@ https://github.com/elastic/beats/compare/v8.2.0\...main[Check the HEAD diff]
 - in module/windows/perfmon, changed collection method of the second counter value required to create a displayable value {pull}32305[32305]
 - Fix and improve AWS metric period calculation to avoid zero-length intervals {pull}32724[32724]
 - Add missing cluster metadata to k8s module metricsets {pull}32979[32979] {pull}33032[33032]
+- Add GCP CloudSQL region filter {pull}32943[32943]
 
 *Packetbeat*
 

x-pack/metricbeat/module/gcp/constants.go

@@ -24,6 +24,7 @@ const (
 	ServiceStorage        = "storage"
 	ServiceFirestore      = "firestore"
 	ServiceDataproc       = "dataproc"
+	ServiceCloudSQL       = "cloudsql"
 )
 
 //Paths within the GCP monitoring.TimeSeries response, if converted to JSON, where you can find each ECS field required for the output event
@@ -81,6 +82,7 @@ const (
 	ComputeResourceLabelZone     = "resource.labels.zone"
 	GKEResourceLabelLocation     = "resource.label.location"
 	StorageResourceLabelLocation = "resource.label.location"
+	CloudSQLResourceLabelRegion  = "resource.labels.region"
 )
 
 // AlignersMapToGCP map contains available perSeriesAligner

x-pack/metricbeat/module/gcp/metrics/metrics_requester.go

@@ -190,6 +190,19 @@ func (r *metricsRequester) getFilterForMetric(serviceName, m string) string {
 			regionsFilter := r.buildRegionsFilter(r.config.Regions, gcp.StorageResourceLabelLocation)
 			f = fmt.Sprintf("%s AND %s", f, regionsFilter)
 		}
+	case gcp.ServiceCloudSQL:
+		if r.config.Region != "" && len(r.config.Regions) != 0 {
+			r.logger.Warnf("when region %s and regions config parameters are both provided, use region", r.config.Region)
+		}
+
+		switch {
+		case r.config.Region != "":
+			region := strings.TrimSuffix(r.config.Region, "*")
+			f = fmt.Sprintf("%s AND %s = starts_with(\"%s\")", f, gcp.CloudSQLResourceLabelRegion, region)
+		case len(r.config.Regions) != 0:
+			regionsFilter := r.buildRegionsFilter(r.config.Regions, gcp.CloudSQLResourceLabelRegion)
+			f = fmt.Sprintf("%s AND %s", f, regionsFilter)
+		}
 	default:
 		if r.config.Region != "" && r.config.Zone != "" {
 			r.logger.Warnf("when region %s and zone %s config parameter "+