typedef struct user {
    char name[MAX_NAME];
    char profile_pic[MAX_NAME];  // This is a *filename*, not the file contents.
    struct post *first_post;
    struct user *friends[MAX_FRIENDS];
    struct user *next;
} User;

int create_user(const char *name, User **user_ptr_add) {
    if(find_user(name, *user_ptr_add) != NULL){
        return 1;
    }
    if(MAX_NAME < strlen(name) + 1){
        return 2;
    }
    else{
        User *new_user = malloc(sizeof(User));
        strcpy(new_user->name, name);
        new_user->profile_pic[0] = '\0';
        new_user->first_post = malloc(sizeof(Post));
        new_user->first_post = NULL;
        if(*user_ptr_add == NULL){
            new_user->next = *user_ptr_add;
            **user_ptr_add = *new_user;
        }
        else{
            User *curr = *user_ptr_add;
            while(curr->next != NULL){
                curr = curr->next;
            }
            new_user->next = curr->next;
            curr->next = new_user;
        }
        return 0;
    }
    return -1;
}
Add a new user to the end of the linked structure