Add non-regression test for serde-reflection

fastpay_core/tests/format.rs

@@ -0,0 +1,12 @@
+// Copyright (c) Facebook Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+#[test]
+fn test_format() {
+    let status = std::process::Command::new("target/debug/generate-format")
+        .current_dir("..")
+        .arg("test")
+        .status()
+        .expect("failed to execute process");
+    assert!(status.success());
+}