int create_user(const char *name, User **user_ptr_add) {

    User *new_user = malloc(sizeof(User));
    strncpy(new_user->name, name, 32);
    new_user -> next = NULL;

    User *curr = *user_ptr_add;
    while(curr->next != NULL){
        curr = curr->next;
    }
    curr->next = new_user;
    return 0;
}
add a new struct user to end of linked list