Even though we don't have a binary dependency on DseAuthProvider, I don't like having the class explicitly specified like this. It would be better if users could specify the classname in the config file. 
See how we used to do this for Thrift transport factory before we switched to native protocol - https://github.com/datastax/cassandra-log4j-appender/blob/99edc6cc23599e3aef7b7e47ae9c677f34b2457b/src/main/java/com/datastax/logging/appender/CassandraAppender.java#L209
Right now, the AuthProvider interface doesn't provide any way to configure it, so all we have to do is to do the isAssignableFrom and instantiate the instance, which will be sufficient for DseAuthProvider. In practice, if someone comes up with another AuthProvider impl which does require further configuration then we can create some kind of AuthProviderFactory interface and have that specified in this config, along with any impl-specific configuration. We don't need that yet, so for now I'd be happy just to remove the DSE-isms.