Cannot update log level of SimpleBrokerMessageHandler using actuator

[nickcaballero-mm]

The log level used by SimpleBrokerMessageHandler cannot be updated via actuator. When debugging, it seems that it uses a org.springframework.core.log.CompositeLog that determines the log levels when creating the instance. This means that the only way to increase the logging level is to stop the server and update the configuration.

As a workaround, we can start the server with a higher logging level and then reduce it using actuator once server has started.

Affects: spring-messaging 5.2.5.RELEASE

[jhoeller]

This should be addressed through #28477 as of 5.3.21 now.