Allow async task to be decorated

[oliemansm]

Is your feature request related to a problem? Please describe.
When using async mode in combination with Spring Security using the Spring Boot starter the SecurityContext is not properly propagated to the async task. Since that task execution is initiated outside of Spring scope the normal task decorators that Spring Security provides for this purpose do not work.

Describe the solution you'd like
We need a similar mechanism here to make sure that the SecurityContext is propagated to the async task.