As a Java developer, I would like to make the Java client model classes implement the Serializable interface. 

Motivation

I am working on a mongodb connector for the [Apache Flink project|https://flink.apache.org/]

Internally, Flink is using java serialization to save the records it is working on in a state which in turn used to recover from failures etc, as well as for passing records between different tasks in the pipeline.
I have noticed the mongodb client model classes are not Serializable for instance, classes such as [WriteModel|https://github.com/mongodb/mongo-java-driver/blob/master/driver-core/src/main/com/mongodb/client/model/WriteModel.java] and its subclasses or the different Options like [ReplaceOptions|https://github.com/mongodb/mongo-java-driver/blob/master/driver-core/src/main/com/mongodb/client/model/ReplaceOptions.java] 

AC

• Make the Java client model classes implement the Serializable interface.