int make_friends(const char *name1, const char *name2, User *head) {
    if (strcmp(name1, name2) == 0){
            return 3;
    }

    if (find_user(name1, head) == NULL || find_user(name2, head) == NULL){
            return 4;
    }

    User *user1 = find_user(name1, head);
    User *friends1 = (*user1).friends;
    User *user2 = find_user(name2, head);
    User *friends2 = (*user2).friends;
    int count1 = 0;
    int count2 = 0;

    while ((*friends1)->next != NULL){
            if (strcmp((*friends1)->name, user2.name) == 0){
                   return 1;
            }
            *friends1 = (*friends1)->next;
            count1++;
            if (count1 > 10){
                    return 2;
            }
    }
    while ((*friends2)->next != NULL){
            *friends2 = (*friends2)->next;
            count2++;
            if (count2 > 10){
                    return 2;
            }
    }
    (*friends1)->next = user2;
    (*friends2)->next = user1;
    return 0;
}


Make two users friends with each other.  This is symmetric - a pointer to
 * each user must be stored in the 'friends' array of the other.
 *
 * New friends must be added in the first empty spot in the 'friends' array.
 *
 * Return:
 *   - 0 on success.
 *   - 1 if the two users are already friends.
 *   - 2 if the users are not already friends, but at least one already has
 *     MAX_FRIENDS friends.
 *   - 3 if the same user is passed in twice.
 *   - 4 if at least one user does not exist.
 *
 * Do not modify either user if the result is a failure.
 * NOTE: If multiple errors apply, return the *largest* error code that applies.