Regression bug - added request header is no longer available in WebErrorHandler

[yanivnahoum]

In Spring Boot 3.4.2/Spring Cloud 2024.0.0, I have a route that forwards gateway requests to a local controller. The route adds a custom header using the AddRequestHeader filter. The local controller method expects a query param. When the parameter is missing, an exception is thrown. It is then caught in a custom WebExceptionHandler that attempts to extract the header from the ServerRequest and log it , but the header is missing. It also includes the header value in the response via a custom ErrorAttributes bean.
This exact same scenario works in Spring Boot 3.3.8/Spring Cloud 2023.0.5

Minimal reproducible example can be found here
Follow the instructions in the README