The DefaultFedletAdapter contains implementation for doFedletSLO and onFedletSLOSuccessOrFailure.
Those methods offer extra functionality that do not belong to a default adapter. There are some issues with it (for example when used in some OpenIG contexts, it will send a POST request that does not succeed and provokes delays with SLO in OpenIG). Default adapter should just be a placeholder.
The current DefaultFedletAdapter code should be renamed, reviewed, fixed if appropriate and documented.