Add a PermissionManager interface as described here:
(possibly there is a better name?)
Implement calls to the PermissionsManager in KafkaApis for the main requests (FetchRequest, ProduceRequest, etc). We will need to add a new error code and exception to the protocol to indicate "permission denied".
Add a server configuration to give the class you want to instantiate that implements that interface. That class can define its own configuration properties from the main config file.
Provide a simple implementation of this interface which just takes a user and ip whitelist and permits those in either of the whitelists to do anything, and denies all others.
Rather than writing an integration test for this class we can probably just use this class for the TLS and SASL authentication testing.