Julia/ SearchLight.Migrations , how to add foreign key?

General Usage
1

I am using Genie Framework and Julia to set up a basic database Migration

This is how my module looks inside the folder db/migrations

module CreateTableRolesUsers

import SearchLight.Migrations: create_table, column, primary_key, add_index, drop_table

function up()
  create_table(:rolesusers) do
    [
      column(:user_id, :string)
      column(:role_id, :integer)
      primary_key(:pk_roleusers)
      
    ]
  end

  add_index(:rolesusers, :role_id)
  add_index(:rolesusers, :user_id)

end

function down()
  drop_table(:rolesusers)
end

end

import SearchLight.Migrations does not offer a method “foreign_key” or “add_foreign_key” like the one for declaring a “primary_key”

how that can be done?