create user balances after register

app/models/user.rb

@@ -34,4 +34,12 @@ class User < ApplicationRecord
   def full_name
     "#{first_name} #{last_name}"
   end
+
+  after_create do
+    create_balances
+  end
+
+  def create_balances
+    CreateUserBalances.new(self).call
+  end
 end

app/services/create_user_balances.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+class CreateUserBalances
+  attr_reader :user
+
+  def initialize(user)
+    @user = user
+  end
+
+  def call
+    return nil if Rails.env.test?
+
+    ActiveRecord::Base.transaction do
+      create_fiat_balance
+      create_balances
+    end
+  end
+
+  private
+
+  def create_fiat_balance
+    FiatBalance.find_or_create_by!(
+      user_id: user.id
+    )
+  end
+
+  def create_balances
+    Currency.in_batches.each do |relation|
+      relation.each do |currency|
+        Balance.find_or_create_by(
+          user_id: user.id,
+          currency_id: currency.id,
+        )
+      end
+    end
+  end
+end