the log wrapper in C/C++ accepts formats

pam-module/examples/logging_example.cpp

@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: Apache-2.0
+// C++ example demonstrating stream-style Rust logging wrapper
+
+#include "../include/rust_backend_ffi.h"
+#include <string>
+
+int main() {
+    rust_init_logging(nullptr);
+
+    std::string user = "bob";
+    bool ok = true;
+
+    RUST_COUT() << "C++ example: user=" << user << " authenticated=" << (ok?"yes":"no") << std::flush;
+    RUST_CERR() << "C++ example: an error message for user=" << user << std::flush;
+
+    return 0;
+}