"Extend environment" approval requests

[Shnitselon]

The environment page now displays yellow indications for environments with "extend environment" requests that are pending approval. This includes:

• A "Cancel Extend" button in the top right corner of the page:
  

• An indication message at the bottom of the page:
  

• And an Extend Request Waiting for Approval activity feed event with an option to cancel the extension request:
  

Note that only the user who requested the extension and the admins can cancel the request.