Convenience functions for many_to_many relationships?

defmodule TestApp.Accounts.User do
  use Ash.Resource, domain: TestApp.Accounts

  actions do
    defaults [:read]

    create :create do
      accept [:email, :first_name, :last_name]
    end

    create :add_to_hub do
      #
      # ?
      # 
    end
  end

  attributes do
    uuid_v7_primary_key :id

    attribute :email, :string do
      allow_nil? false
      public? true
    end
  end

  relationships do
    many_to_many :hubs, TestApp.Hubs.Hub do
      through TestApp.Hubs.UsersToHubs
      source_attribute_on_join_resource :user_id
      destination_attribute_on_join_resource :hub_id
    end
  end
end


defmodule TestApp.Hubs.UsersToHubs do
  use Ash.Resource, domain: TestApp.Hubs

  actions do
    defaults [:read, :destroy, create: :*, update: :*]
  end

  attributes do
    create_timestamp :inserted_at
    update_timestamp :updated_at
  end

  relationships do
    belongs_to :hub,
               TestApp.Hubs.Hub,
               primary_key?: true,
               allow_nil?: false

    belongs_to :user,
               TestApp.Accounts.User,
               primary_key?: true,
               allow_nil?: false
  end
end