In Spring Framework 5.x with Jetty 9, the reactive
JettyRequestUpgradeStrategy was able to initialize Jetty's WebSocket
infrastructure itself. With Jetty 10 this is no longer possible and
Boot must perform the initialization as part of preparing the
reactive JettyWebServer.
This commit updates the reactive WebSocket auto-configuration to
initialize Jetty's WebSocket infrastructure as part of creating the
reactive JettyWebServer.
Fixes gh-33347
39c382713b