Support omit null values in OData 4 JSON connector
The OData4 protocol defines options to reduce data volume by omitting null values. It requires the consumer to set the Prefer HTTP header to omit-vales=nulls and OData-MaxVersion to 4.0. The producer then replies by saying it acknowledges omitting null values.
The omittance reduces data volume depending on data source between 10% and 95%.
