Status messages styling broken with big pipe after 10.3 drupal core update

[vever001]

This is a preliminary report (will update once/if we start working on this).

After updating to drupal core 10.3, if the website uses big_pipe, it seems status messages are no longer styled (bypassing status-messages.html.twig) and show up unstyled/raw.
This seems to come from https://www.drupal.org/project/drupal/issues/3379885 which already has some reports of similar cases.

This may require implementing Drupal.theme.message as per https://www.drupal.org/project/drupal/issues/3456176#comment-15692107

[drishu]

needs more info, like steps to reproduce including what is expected versus what is actually.

[vever001]

This is very easy to reproduce:

• Install clean drupal core 10.2.x (standard profile*), oe_bootstrap_theme + helper, set theme as default
• Login as superadmin, add a new page, notice the status message is OK/styled
  
• Now update to 10.3.x, create or update a basic page, notice status messages are unstyled, broken
  

3379885 was introduced in 10.3.0
*Big pipe comes enabled by default with the standard profile