Make the creation of terms for a entity a service

Problem/Motivation

Using a custom submit handler is not the best approach. We should convert the submit handler to a service that can be re-used and manipulated where-ever we want.

Steps to reproduce

Proposed resolution

Create a service called EatEventSubscriber that gives us flexibilty and control to utilise EAT when we want.

Remaining tasks

User interface changes

API changes

Data model changes