extract email assets

db/migrate/20260628120000_create_email_message_assets.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+class CreateEmailMessageAssets < ActiveRecord::Migration[8.1]
+  def change
+    create_table :email_message_assets do |t|
+      t.references :account, null: false, foreign_key: true, index: false
+      t.text :data, null: false
+      t.string :sha1, null: false
+      t.timestamps
+    end
+
+    add_index :email_message_assets, %i[account_id sha1], unique: true
+  end
+end