feat: support composite type in maps during serialization

[Meghajit]

Summary
As of now, Dagger doesn’t have the support just yet to serialize composite types in map values to kafka. Both the key and value are casted to String. This is the relevent piece of code which is doing this at the moment:

   builder.addRepeatedField(fieldDescriptor,
                    mapEntry.toBuilder()
                            .setKey((String) inputRow.getField(0))
                            .setValue((String) inputRow.getField(1))
                            .buildPartial());

This card is to support serialization of complex map values into the appropriate wire format to kafka.