Add new warn_println() fn

server/src/util.rs

@@ -7,3 +7,7 @@ pub fn print_copyright_notice() {
 pub fn notice_println(msg: impl Into<String>) {
     println!("{}", msg.into().green().bold());
 }
+
+pub fn warn_println(msg: impl Into<String>) {
+    eprintln!("{}", msg.into().yellow().bold());
+}