int create_user(const char *name, User **user_ptr_add) i{
        if (strlen(name) > 31){
                return 2;
        } else {
                while (**user_ptr_add->next != NULL){
                        if (strcmp(**user_ptr_add, name)){
                                return 1;
                        }
                        **user_ptr_add++;
                }
                *user_ptr_add->next = malloc(sizeof(User));
                strcpy(*user_ptr_add->next->name, name);
                *user_ptr_add->next->next = NULL;
                return 0;
}


/*
 * Create a new user with the given name.  Insert it at the tail of the list
 * of users whose head is pointed to by *user_ptr_add.
 *
 * Return:
 *   - 0 if successful
 *   - 1 if a user by this name already exists in this list
 *   - 2 if the given name cannot fit in the 'name' array
 *       (don't forget about the null terminator)
 */