Customers can now complete eCommerce billing information without entering a postal code. This reduces checkout friction for customers in locations where postal codes are not commonly used or necessary.

Fix: #985
Made postal code field of billing information optional in eCommerce module.

Tips now wait for message discussions to finish loading before appearing, so users see guidance in the right place at the right time. The update also improves how tips adjust after page changes or window resizing, reducing misplaced or confusing help prompts.

- Override message_fetch from mail.Thread and fire an event when the messages are loaded. This is necessary for tips on the chatter
- Override render_value form web.form.FieldStatus : Call reposition() when FieldStatus is done rendering.
- Tip.reposition() method
- Handle window resize event