feat: add database_id attribute to resource model and update related functions

stackit/internal/services/postgresflexalpha/database/functions.go

@@ -3,6 +3,7 @@ package postgresflexalpha
 import (
 	"context"
 	"fmt"
+	"strings"
 
 	postgresflex "tf-provider.git.onstackit.cloud/stackit-dev-tools/terraform-provider-stackitprivatepreview/pkg_gen/postgresflexalpha"
 )
@@ -79,3 +80,12 @@ func getDatabase(
 
 	return nil, fmt.Errorf("database not found for instance %s", instanceId)
 }
+
+// cleanString removes leading and trailing quotes which are sometimes returned by the API.
+func cleanString(s *string) *string {
+	if s == nil {
+		return nil
+	}
+	res := strings.Trim(*s, "\"")
+	return &res
+}