refactor: simplify Node SSR parsing and validation

internal/transaction/node_ssr_container_deployment.go

@@ -88,9 +88,17 @@ func validateNodeSsrContainerDeployment(deployment NodeSsrContainerDeployment) e
 	if deployment.ActivePort != 18910 && deployment.ActivePort != 28910 {
 		return fmt.Errorf("Node SSR container deployment port must be 18910 or 28910: %d", deployment.ActivePort)
 	}
-	for name, value := range map[string]string{"container name": deployment.ContainerName, "image digest": deployment.ImageDigest, "container ID": deployment.ContainerID} {
-		if value == "" || strings.TrimSpace(value) != value {
-			return fmt.Errorf("exact Node SSR container %s is required", name)
+	fields := []struct {
+		name  string
+		value string
+	}{
+		{name: "container name", value: deployment.ContainerName},
+		{name: "image digest", value: deployment.ImageDigest},
+		{name: "container ID", value: deployment.ContainerID},
+	}
+	for _, field := range fields {
+		if field.value == "" || strings.TrimSpace(field.value) != field.value {
+			return fmt.Errorf("exact Node SSR container %s is required", field.name)
 		}
 	}
 	return nil