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

    if (*user_ptr_add == NULL){
        if (strlen(name) > 31){
            return 2; 
        }
        User *user_ptr_add = malloc(sizeof(User));
        strcpy(user_ptr_add->name, name);
        user_ptr_add->next = NULL;
        return 0;

    }

    User *curr = NULL;
    User *curr_next = *user_ptr_add;

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

    if (strlen(name) > 31){
        return 2;
    }

    User *created_new_user = malloc(sizeof(User));
    strcpy(created_new_user->name, name);
    curr->next = created_new_user;
    created_new_user->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)