User *find_user(const char *name, const User *head) {
    User *curr = (User*) head;
    while (curr != NULL){
        if (strcmp(curr->name, name) == 0){
            return curr;
        }
        curr = curr->next;
    }
    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.