add createStakeOrder mutation

app/graphql/inputs/create_stake_order_attributes_input.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+module Inputs
+  class CreateStakeOrderAttributesInput < Types::BaseInputObject
+    argument :currency_id, ID, required: true
+    argument :pool_name, String, required: true
+    argument :amount, String, "Amount to be paid", required: true
+  end
+end