How to add (intercept?) messages in the broker before and after they are serialized?

["del Castillo Perez, Daniel" <da...@vonage.com.INVALID>]

Hello there,

I'm facing a challenge at the moment where I need to somehow extend the
brokers so I can make decisions on the messages (whether they should be
discarded or not) on the server side. I've read the documentation but I
haven't seen a way of doing this so I'm starting to look into the code.

I wonder if anyone can shed some light here as I don't know where to look.
Any pointers would be really appreciated - either source code or something
else.

Best regards,
Daniel