Add empty WHN markdown field and update existing live forms

db/migrate/20231116142411_add_what_happens_next_markdown_to_forms.rb

@@ -0,0 +1,23 @@
+class AddWhatHappensNextMarkdownToForms < ActiveRecord::Migration[7.0]
+  def change
+    add_column :forms, :what_happens_next_markdown, :text
+
+    reversible do |direction|
+      Form.find_each do |form|
+        if form.made_live_forms.present?
+          made_live_form = form.made_live_forms.last
+          form_blob = JSON.parse(made_live_form.json_form_blob, symbolize_names: true)
+
+          direction.up do
+            form_blob[:what_happens_next_markdown] = nil
+          end
+          direction.down do
+            form_blob.delete(:what_happens_next_markdown)
+          end
+
+          made_live_form.update!(json_form_blob: form_blob.to_json)
+        end
+      end
+    end
+  end
+end