Evaluate the impact on existing guides, whether the affected content is upstream-downstream (and the corresponding 8/14 cut-off date) or downstream only, and any follow up steps.

Affected version: 3.9

SME: guillaume.smet 

Resources:

• https://github.com/quarkusio/quarkus/pull/39159 
• An overview of the changes can be found in the migration guide: https://github.com/quarkusio/quarkus/wiki/Migration-Guide-3.9#resteasy-reactive-extensions-renamed-to-quarkus-rest .