Document maintenance mode and recommended migrations. Fixes gh-968

Author: OlgaMaciaszek

docs/modules/ROOT/pages/intro.adoc

@@ -4,3 +4,5 @@
 This project provides OpenFeign integrations for Spring Boot apps through autoconfiguration
 and binding to the Spring Environment and other Spring programming model idioms.
 
+WARNING: As announced in https://spring.io/blog/2022/12/16/spring-cloud-2022-0-0-codename-kilburn-has-been-released#spring-cloud-openfeign-feature-complete-announcement[Spring Cloud 2022.0.0 release blog entry], we're now treating the Spring Cloud OpenFeign project as feature-complete. We are only going to be adding bugfixes and possibly merging some small community feature PRs. We suggest migrating over to https://docs.spring.io/spring-framework/reference/integration/rest-clients.html#rest-http-interface[Spring Interface Clients] instead.
+

docs/modules/ROOT/pages/spring-cloud-openfeign.adoc

@@ -807,7 +807,10 @@ protected interface DemoFeignClient {
 
 [[reactive-support]]
 === Reactive Support
-As the https://github.com/OpenFeign/feign[OpenFeign project] does not currently support reactive clients, such as https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/reactive/function/client/WebClient.html[Spring WebClient], neither does Spring Cloud OpenFeign.We will add support for it here as soon as it becomes available in the core project.
+As the https://github.com/OpenFeign/feign[OpenFeign project] does not currently support reactive clients, such as https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/reactive/function/client/WebClient.html[Spring WebClient], neither does Spring Cloud OpenFeign.
+
+SinceSpring Cloud OpenFeign project is now considered feature-complete, we're not planning on adding support even if it becomes available in the upstream project. We suggest migrating over to https://docs.spring.io/spring-framework/reference/integration/rest-clients.html#rest-http-interface[Spring Interface Clients] instead. Both blocking and reactive stacks are supported there.
+
 
 Until that is done, we recommend using https://github.com/Playtika/feign-reactive[feign-reactive] for Spring WebClient support.