Feature/127 immutability policy for test

[barrjam]

A CI/CD pipeline needs to clean up all resources after a test deployment.

• Setting an 'immutability policy' means it is impossible to delete Blob Containers
• This change disables the the 'immutability policy' if the resource group name contains the word 'test'

I've set this as a draft pull request but could you give me feedback to see if this is 1) okay and 2) are there any other issues like this?

Thx

[augustincolle-digit]

Approved change