Implemented leaving a gamenight on the server/database side

gamenight-cli/src/flows/view_gamenight.rs

@@ -23,7 +23,7 @@ impl ViewGamenight {
 
 fn vec_user_to_usernames_string(users: Vec<User>) -> String {
     
-    let string_list: Vec<String> = users.iter().map(|x| {x.username.clone()}).collect();
+    let string_list: Vec<String> = users.iter().map(|x| {format!("{}", x)}).collect();
     string_list.join(", ")
 }