azurerm_postgresql_flexible_server - support importing PGSQL replica servers (hashicorp#30350)

Co-authored-by: Matt Heitzenroder <[email protected]>

Author: roder

internal/services/postgres/postgresql_flexible_server_resource.go

@@ -692,6 +692,7 @@ func resourcePostgresqlFlexibleServerRead(d *pluginsdk.ResourceData, meta interf
 			d.Set("zone", props.AvailabilityZone)
 			d.Set("version", pointer.From(props.Version))
 			d.Set("fqdn", props.FullyQualifiedDomainName)
+			d.Set("source_server_id", props.SourceServerResourceId)
 
 			// Currently, `replicationRole` is set to `Primary` when `createMode` is `Replica` and `replicationRole` is updated to `None`. Service team confirmed it should be set to `None` for this scenario. See more details from https://github.com/Azure/azure-rest-api-specs/issues/22499
 			d.Set("replication_role", d.Get("replication_role").(string))