chore: Whatsapp templates fix for 360 dialog (#3479)

Fixes: #3426

db/migrate/20211129120040_add_templates_to_whatsapp_channel.rb

@@ -0,0 +1,15 @@
+class AddTemplatesToWhatsappChannel < ActiveRecord::Migration[6.1]
+  def up
+    change_table :channel_whatsapp, bulk: true do |t|
+      t.column :message_templates, :jsonb, default: {}
+      t.column :message_templates_last_updated, :datetime
+    end
+  end
+
+  def down
+    change_table :channel_whatsapp, bulk: true do |t|
+      t.remove :message_templates
+      t.remove :message_templates_last_updated
+    end
+  end
+end