Recommend ObjectProvider as alternative to @Lazy for optional dependencies

Closes gh-27649

spring-context/src/main/java/org/springframework/context/annotation/Lazy.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -47,6 +47,11 @@ import java.lang.annotation.Target;
  * or {@link javax.inject.Inject}: In that context, it leads to the creation of a
  * lazy-resolution proxy for all affected dependencies, as an alternative to using
  * {@link org.springframework.beans.factory.ObjectFactory} or {@link javax.inject.Provider}.
+ * Please note that such a lazy-resolution proxy will always be injected; if the target
+ * dependency does not exist, you will only be able to find out through an exception on
+ * invocation. As a consequence, such an injection point results in unintuitive behavior
+ * for optional dependencies. For a programmatic equivalent, allowing for lazy references
+ * with more sophistication, consider {@link org.springframework.beans.factory.ObjectProvider}.
  *
  * @author Chris Beams
  * @author Juergen Hoeller