This method is creating the JSON array manually because of a bug in the object mapper where:
-> When the object mapper serializes 1 MeasurementCollectionJob it works fine
-> When the object mapper serializes a list of Measurement CollectionJob it ommits the "@type" field
As a result when de-serializing the list of MeasurementCollectionJob this error comes-up:
com.fasterxml.jackson.databind.exc.InvalidTypeIdException: Could not resolve subtype of [simple type, class org.etsi.osl.tmf.pm628.model.MeasurementCollectionJob]: missing type id property '@type'