Methods with implicit pagination should accept an include function

[theckman]

Related to #294 #295, in v2 we should investigate having the paginated methods accept a func(T) bool where, where T is the type of item being paginated and the bool is whether the item should be included. For example,

func ListUsersPaginated(ctx context.Context, include func(User) bool) ([]User, error) { 
    if include == nil {
        include = func(User) bool { return true }
    }

    var collection []User

    // ...

    for _, u := range users {
        if include(u) {
            collection = append(collection, u)
        }
    }

    return collection, nil
}