It seems, that JGroups SASL configuration is little bit misleading for users. The documentation should stress that CallbackHandler classes have to be implemented/provided by users and the class names are just examples, which are not contained in JDG release.
The doucumentation should also clearly explain what's needed to implement the class (for example a full description of the API that must be implemented).
Gemma, could you please focus on this bug as the priority? I'd like to release this ASAP once we have sign off from the relevant stakeholders.
Adding Needinfo Vojtech for review.
setting needinfo for QA ack.