rom aggregate with join table

aggregate.rb

require 'pp'
require 'pry'
require 'rom'
require 'rom-sql'
require 'rom-repository'
require 'dry-struct'

rom = ROM.container(:sql, 'sqlite::memory') do |conf|
  conf.default.create_table(:movies) do
    primary_key :id
    column :title, String, null: false
  end

  conf.default.create_table(:actors) do
    primary_key :id
    column :name, String, null: false
  end

  conf.default.create_table(:roles) do
    primary_key :id
    foreign_key :actor_id, :actors, null: false
    foreign_key :movie_id, :movies, null: false
    column :name, String, null: false
  end

  conf.relation(:actors) do
    schema(infer: true) do
      associations do
        has_many :roles
      end
    end

    view(:for_movies, [:actor_id, :actor_name, :name, :movie_id]) do |movies|
      prefix(:actor)
        .qualified
        .select_append(:roles__name, :roles__movie_id)
        .inner_join(:roles, roles__actor_id: :actors__id)
        .where(roles__movie_id: movies.pluck(:id))
    end
  end

  conf.relation(:roles) do
    schema(infer: true) do
      associations do
        belongs_to :movie
        belongs_to :actor
      end
    end
  end

  conf.relation(:movies) do
    schema(infer: true) do
      associations do
        has_many :roles
        has_many :actors, through: :roles
      end
    end
  end
end

DB = rom.gateways[:default].connection
movie_id = DB[:movies].insert(title: "Star Wars")
actor_id = DB[:actors].insert(name: "Peter Mayhew")
DB[:roles].insert(movie_id: movie_id, actor_id: actor_id, name: "Chewbacca")

class MovieRepo < ROM::Repository[:movies]
  relations :actors

  def with_casts
    movies.combine_children(many: { casts: actors.for_movies })
  end
end

pp MovieRepo.new(rom).with_casts.one