Add concept of a primary identifier in addition to last seen identifier

I as user would like to be able to control what identifier value is considered as the primary one, so that we can be sure that customer is always contacted with the email that they have selected. I want to be able to set this manually via UI or API.

When we have a case where customer has multiple emails addresses linked to them, but we have customer profile where they have selected the primary email address they use, we want to be able to make sure that all communications use the primary email. In this case the last seen email may or may not be the one that customer has selected and that is the only one we can access in ODP.