Email alerts for new content creation

Hi All,

I am working on a plugin that will allow users to register for email alerts when new content is CREATED for a object type, in this case "about".  How do I do this as I'm not sure my approach is correct?

I looked into


Which is fine but how do I create the relationship between the user and
object-type when the relationship is based on two existing GUID?

Any advice would be appreciated.