Test Plan automatic association to Tests through Test Executions

As a user, I should be able to associate Tests to Test Plans automatically from Test Executions.
Nowadays, Tests must be added explicitly to the Test Plan.
Possible usage senarios:

• create Test Executions and associate them to the Test Plan and have the Tests automatically in the Test Plan, without having to manage the Tests inside the Test Plan

Impacts:

• REST API
• add/remove Tests from Test Executions will eventually affect the Test Plan (it depends, if that Test is or not in other Test Executions related to that Test Plan)