extract email assets

app/models/account.rb

@@ -24,6 +24,7 @@ class Account < ApplicationRecord
   has_many :encrypted_configs, dependent: :destroy
   has_many :account_configs, dependent: :destroy
   has_many :email_messages, dependent: :destroy
+  has_many :email_message_assets, dependent: :destroy
   has_many :templates, dependent: :destroy
   has_many :template_folders, dependent: :destroy
   has_one :default_template_folder, -> { where(name: TemplateFolder::DEFAULT_NAME) },