We are receiving a consistent error on the test suite running the `AuthorizationPropertiesIT`. Test failing is `RESTAuthorizationTest.testRestAdminsMustAccessBackupsAndRestores` with the message:

18:45:53,158 INFO  [o.i.CONTAINER] [o.i.s.s.a.AuthorizationPropertiesIT#0] STDOUT: 16:45:53,156 WARN  [o.i.PERSISTENCE] ISPN000559: Cannot marshall 'class org.infinispan.multimap.impl.HashMapBucket' java.lang.IllegalArgumentException: No marshaller registered for object of Java type org.infinispan.commons.marshall.WrappedByteArray : WrappedByteArray[\k\e\y\1 (4 bytes)] 

The issue happens while creating the backup, where the values stored on the HashMapBucket are not stored properly.

The initial approach here was using DataConversion to transform objects. This makes everything harder since the conversion class needs to be passed as arguments every time. We can simplify by creating a wrapper class for multimap, which can be serialized properly and offers a correct implementation for equals/hashCode for the wrapped element.