Previous to the introduction of the optional substitution type (base type) in SDC-3759, the system would always add a base type to a Service. With the change, the system would only add a base type if it was send in the API call. This introduced a regression in the API for calls that were not providing the substitution type to create a service.

Set a default substitution type when none is provided during the creation of a service with a category that requires a base type. For categories with optional substitution type, no base type can be forced.