Reactive endpoints using RouterFunction.nested with version predicate only supports one nested route

[s5jonathan]

Describe the bug

Using RequestPredicates.version as a predicate for RouterFunctions.nest only works for the first nested route. I think the issue stems from the fact that AbstractRouterFunctionVisitor::commonRoute sets this.version = null causing the version to work for the first nested route but not to be set for future nested routes.

To Reproduce

public RouterFunction<ServerResponse> router3() {
    HandlerFunction<ServerResponse> handler = request -> ServerResponse.accepted().build();
    return RouterFunctions.nest(path("/api/{version}"),
            RouterFunctions.nest(version("v1"),
                route().GET("/foo", handler, ops -> ops.operationId("getFooV1")).build()
                .and(route().GET("/bar", handler, ops -> ops.operationId("getBarV1")).build())
            .andNest(version("v2"),
                route().GET("/foo", handler, ops -> ops.operationId("getFooV2")).build()
                .and(route().GET("/bar", handler, ops -> ops.operationId("getBarV2")).build()))));
}

With path segment routing, this currently generates the following:

/api/v1/foo
/api/v2/foo
/api/{version}/bar

Expected behavior

/api/v1/foo
/api/v1/bar
/api/v2/foo
/api/v2/bar

• What version of spring-boot you are using? 4.0.5
• What modules and versions of springdoc-openapi are you using? springdoc-openapi-starter-webflux-ui 3.0.3