Add customisable policies for whitelisting messages

[oskardudycz]

Per discussion: #7 (comment)

I understand the security concern, but I'm not sure if it wouldn't be good to add an option to register the default resolution strategy for unresolved types. Then user could decide if they want to take the risk and add it not need to do manual.

Of course, they could use tools like ScrutR for conventional-based registration, but that'll require either some marker interfaces or class or folder naming strategies (which I'm personally not a big fan of).