add user document model

db/migrate/20210805000225_create_user_documents.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+class CreateUserDocuments < ActiveRecord::Migration[6.1]
+  def change
+    create_table(:user_documents) do |t|
+      t.string(:status, null: false)
+      t.references(:user, null: false, foreign_key: true)
+
+      t.timestamps
+    end
+  end
+end