product.rb

class Product
  field :traits, type: Array, default: []
  
  after_initialize :load_traits!
  on_save :validates_methods
  
  def load_traits!
    self.traits.each do |trait|
      self << class
        self.send(:include, trait.camelize.constantize)
      end
    end
  end
  
  def validates_methods
    [:settlement_periods].all?{ |m| self.respond_to?(m) }
  end
end

product_migration.rb

Product.new(name: "Foo", traits: [:nymex_gas])

settlement_concepts.rb

module SettlementConcepts
  module LastDayOfMonth
    def settlement_periods(trade)
      [(trade.tenor_start - 1.month).end_of_month]
    end
  end
  
  module LastDayOfEveryMonthInTenor
    def settlement_periods(trade)
      (trade.tenor_start..trade.tenor_end).to_a.map(&:end_of_month).uniq
    end
  end
end

settlement_service.rb

class SettlementService
  include Molecule::Services::Base
  
  def call(trades, options=nil)
    options ||= {}
    
    Hash[*trades.map do |trade|
      [trade, trade.settlement_periods]
    end.flatten]
  end
end

trade.rb

class Trade
  delegate :settlement_periods, to: :product
end

traits.rb

module NymexGas
  include SettlementConcepts::LastDayOfMonth
  include PositionConcepts::CalculateMonthly
  include PositionConcepts::SomethingElse
end

module Power
  include SettlementConcepts::DayOfFlow
  include PositionConcepts::GroupByBlock
end

module Ercot
  include PositionConcepts::FullDayBlock
  include PositionConcepts::OnPeakAtEightInTheMorning
end

module PJM
  include PositionConcepts::FullDayBlock
  include PositionConcepts::OnPeakAtSevenInTheMorning
end