obdev/db/migrate/20240117024001_create_join_table_participant_program.rb

class CreateJoinTableParticipantProgram < ActiveRecord::Migration[7.1]
  def change
    create_join_table :participants, :programs do |t|
      # t.index [:participant_id, :program_id]
      # t.index [:program_id, :participant_id]
    end
  end
end