---
features:
  - Adds a new "immutable" boolean field to the parameters section in
    a HOT template.  This gives template authors the ability to mark
    template parameters as immutable to restrict updating parameters
    which have destructive effects on the application.  A value of
    True results in the engine rejecting stack-updates that include
    changes to that parameter.  When not specified in the template,
    "immutable" defaults to False to ensure backwards compatibility
    with old templates.