This container describes a key-value pair used in a Data Transfer Object. The key-value pair corresponds to a service attribute.
The KeyValue.value field can be a basic type such as string, boolean or int, or it can have a type defined in the attribute's
namespace. For instance, in the com.genesyslab.ail.ws.outbound namespace, the OutboundChainDTO.data field can be one of the
object types listed in the outbound.chain attributes definitions, which include OutboundChainReason, CampaignMode, TreatmentType,
or OutboundEventType.