Add preferred_zone in clone context of sql database instance resource (#8990)

Author: ibhaskar2

mmv1/third_party/terraform/services/sql/resource_sql_database_instance.go.erb

@@ -946,6 +946,11 @@ is set to true. Defaults to ZONAL.`,
 							DiffSuppressFunc: tpgresource.TimestampDiffSuppress(time.RFC3339Nano),
 							Description:      `The timestamp of the point in time that should be restored.`,
 						},
+						"preferred_zone": {
+    						Type:        	  schema.TypeString,
+    						Optional:         true,
+    						Description:      `(Point-in-time recovery for PostgreSQL only) Clone to an instance in the specified zone. If no zone is specified, clone to the same zone as the source instance.`,
+   						},
 						"database_names": {
 							Type:             schema.TypeList,
 							Optional:         true,
@@ -1317,6 +1322,7 @@ func expandCloneContext(configured []interface{}) (*sqladmin.CloneContext, strin
 
 	return &sqladmin.CloneContext{
 		PointInTime: _cloneConfiguration["point_in_time"].(string),
+		PreferredZone: _cloneConfiguration["preferred_zone"].(string),
 		DatabaseNames: databaseNames,
 		AllocatedIpRange: _cloneConfiguration["allocated_ip_range"].(string),
 	}, _cloneConfiguration["source_instance_name"].(string)

mmv1/third_party/terraform/services/sql/resource_sql_database_instance_test.go

@@ -3727,6 +3727,7 @@ resource "google_sql_database_instance" "instance" {
   clone {
     source_instance_name = data.google_sql_backup_run.backup.instance
     point_in_time = data.google_sql_backup_run.backup.start_time
+	preferred_zone = "us-central1-b"
   }
 
   deletion_protection = false

mmv1/third_party/terraform/website/docs/r/sql_database_instance.html.markdown

@@ -486,6 +486,8 @@ The optional `clone` block supports:
 
     A timestamp in RFC3339 UTC "Zulu" format, with nanosecond resolution and up to nine fractional digits. Examples: "2014-10-02T15:01:23Z" and "2014-10-02T15:01:23.045123456Z".
 
+* `preferred_zone` - (Optional) (Point-in-time recovery for PostgreSQL only) Clone to an instance in the specified zone. If no zone is specified, clone to the same zone as the source instance. [clone-unavailable-instance](https://cloud.google.com/sql/docs/postgres/clone-instance#clone-unavailable-instance)
+
 * `database_names` - (Optional) (SQL Server only, use with `point_in_time`) Clone only the specified databases from the source instance. Clone all databases if empty.
 
 * `allocated_ip_range` -  (Optional) The name of the allocated ip range for the private ip CloudSQL instance. For example: "google-managed-services-default". If set, the cloned instance ip will be created in the allocated range. The range name must comply with [RFC 1035](https://tools.ietf.org/html/rfc1035). Specifically, the name must be 1-63 characters long and match the regular expression [a-z]([-a-z0-9]*[a-z0-9])?.