Implement infinite scroll

[skryukov]

This PR introduces infinite scroll functionality to Inertia Rails. It comes with out of the box support for Pagy & Kaminari gems and ability to register custom scroll metadata adapters.

Pagy

class UsersController < ApplicationController
  include Pagy::Backend

  def index
    pagy, records = pagy(User.all)

    render inertia: {
      users: InertiaRails.scroll(pagy) { records.as_json(...) }
    }
  end
end

Kaminari

class UsersController < ApplicationController
  def index
    users = User.page(params[:page])

    render inertia: {
      # Pass collection to the scroll method to extract pagination metadata
      users: InertiaRails.scroll(users) { users.as_json(...) },
    }
  end
end

Manual

class UsersController < ApplicationController
  def index
    meta, users = paginate(User.order(:name))

    render inertia: {
      users: InertiaRails.scroll(meta) { users.as_json(...) }
    }
  end

  private

  PER_PAGE = 20

  def paginate(scope, page_param: :page)
    page = [params.fetch(page_param, 1).to_i, 1].max

    records = scope.offset((page - 1) * PER_PAGE).limit(PER_PAGE + 1)

    meta = {
      page_name: page_param.to_s,
      previous_page: page > 1 ? page - 1 : nil,
      next_page: records.length > PER_PAGE ? page + 1 : nil,
      current_page: page
    }

    [meta, records.first(PER_PAGE)]
  end
end

For more info see the provided docs.