Avoid using deprecated ListenableFuture interface

This rule flags classes that implement the ListenableFuture interface. In SpringFramework 6.0 the ListenableFuture interface has been deprecated in favor of the CompletableFuture interface.

Users migrating to SpringFramework 6.0 should use the CompletableFuture interface, since the ListenableFuture interface will be removed in future.

For more information, see the following resources:

• Spring Framework 6.0 Release Notes
• Spring Github Issue: Deprecate ListenableFuture in favor of CompletableFuture
• ListenableFuture documentation