void list_users(const User *curr) {
    // WHAT IF CURR IS NULL, DO WE HAVE TO ACCOUNT FOR THAT CASE??

    // case where curr is no null
    while (curr != NULL) {
        printf("%s\n",curr->name);
        curr = curr->next;
    }
}
rint the usernames of all users in the list starting at curr.
 * Names should be printed to standard output, one per line.