add createStakeOrder mutation

db/migrate/20210816174637_add_currency_to_stake_order.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+class AddCurrencyToStakeOrder < ActiveRecord::Migration[6.1]
+  def change
+    add_reference(:stake_orders, :currency, foreign_key: true)
+  end
+end