User *find_user(const char *name, const User *head) {
    User *curr = (User *) head;
    if (curr != NULL) {
        while (curr->next != NULL) {
            if(strcmp(curr->name, name) == 0) {
                return curr;
            }
        curr = curr->next;
        }
        if(strcmp(curr->name, name) == 0) {
            return curr;
        }
    }
    return NULL;
}
Return a pointer to the user with this name in
 * the list starting with head. Return NULL if no such user exists.
 *
 * NOTE: You'll likely need to cast a (const User *) to a (User *)
 * to satisfy the prototype without warnings.