title: Referencing a Managed Service Identity in ARM-template deploy
body: <p>When deploying a Microsoft.Web resource with the new MSI feature the principleId GUID for the created user is visible after deployment. Screenshot below shows the structure in the ARM-template.</p>
  
  <p><a href="https://i.stack.imgur.com/nr4b8.png" rel="noreferrer"><img src="https://i.stack.imgur.com/nr4b8.png" alt="enter image description here"></a></p>
  
  <p>What would be the best way to fetch this GUID later in the pipeline to be able to assign access rights in (for instance) Data Lake Store?</p>
  
  <p>Is it possible to use any of the existing ARM template functions to do so?</p>