Add code of conduct button and fix invalid display names

src/database/models.rs

@@ -1914,7 +1914,7 @@ impl<'a> Object<'a> for Participant {
 
 fn make_name_valid(name: String) -> String {
     if name.len() == 1 {
-        format!("{name}⠀⠀")  // Add two invisible characters
+        format!("{name}-")
     } else if name.len() > 80 {
         format!("{name:.80}")
     } else {