Messages sent with redirect responses cannot be server-rendered

Problem

Unlike traditional Drupal lupus CE renderer sends drupal-messages with redirect responses. This is a feature, that was introduced to help with static site generation: When the redirect target is pre-generated, this is the only way the drupal-message will end-up in the frontend.

This approach is great for SSG and fine with SSR on sub-sequent client-side rendered API requests. However, for server-rendered requests the server cannot properly return a redirect + set the message (without doing workarounds like setting a cookie and reading it later)

Proposed resolution

Support both, sending the message with next requests like traditional Drupal OR sending the message the redirect response. Make it configurable. New installs should fit the SSR behaviour, for BC existing installs should get it configured to send the message with the redirect.

Remaining tasks

User interface changes

API changes

Data model changes