Story https://jira.onap.org/browse/SDC-3673 introduces the possibility to create a model based on a VSP import where that model extends from a normative model (for example extends an ETSI model). 

Currently all models defined are displayed to the user (for example at VSP onboarding, service creation etc). However it it not desirable to expose to the user any models created that are package specific. 

This story is to introduce the concept of model types and filter what is exposed to the user based on the model type.

The allowed values of model type shall be:

• normative - indicating a model that is normative in its nature, for example an ETSI model
• normative-extension -indicating where a model is an extension of a normative model, for example a model created for a VSP package that extends an ETSI model

There may possible be other values in the future