Validating currency when setting field

[DanielPechersky]

I have an ActiveRecord that looks like

class CheckoutSession < ApplicationRecord
  register_currency :usd
  
  monetize :total_amount_cents
end

with a migration that looks like

class CreateCheckoutSessions < ActiveRecord::Migration[7.0]
  def change
    create_table :checkout_sessions do |t|
      t.monetize :total_amount, currency: {present: false}

      t.timestamps
    end
  end
end

I'd like to force the currency of CheckoutSession.total_amount to be USD so that if I do
CheckoutSession.create!(total_amount: Money.from_cents(100, "CAD"))
or
session.total_amount = Money.from_cents(100, "CAD")
I get an exception.

How would I go about doing this?