is curr->name a string
int create_user(const char *name, User **user_ptr_add) {
        if (strlen(name) >= MAX_NAME) {
                return 2;
        }

        // make new user
        User *new_user = malloc(sizeof(User));
        strncpy(new_user->name, name, sizeof(MAX_NAME - 1));
        (new_user->name)[MAX_NAME - 1] = '\0';

        User *curr = *user_ptr_add;
        if (curr == NULL) {
                curr = new_user;
                new_user->next = NULL;
                return 0;
        }

        while (curr->next != NULL) {
                if (strcmp(name, curr->name) == 0) {
                        return 1;
                }
                curr = curr->next;
        }

        curr->next = new_user;
        new_user = NULL;
        return 0;
}