add template variables

db/migrate/20250912090605_add_template_variables.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class AddTemplateVariables < ActiveRecord::Migration[8.0]
+  def change
+    add_column :templates, :variables_schema, :text
+    add_column :submissions, :variables_schema, :text
+    add_column :submissions, :variables, :text
+  end
+end