Describe exceptions to an object's policy setting.

The intent of this method is to explain and inform users about special cases which override configured policy settings. If this object has any such exceptions, explain them by returning one or more human-readable strings which describe the exception in a broad, categorical way. For example:

• "The owner of an X can always view and edit it."
• "Members of a Y can always view it."

You can return null, a single string, or a list of strings.

The relevant capability to explain (like "view") is passed as a parameter. You should tailor any messages to be relevant to that capability, although they do not need to exclusively describe the capability, and in some cases being more general ("The author can view and edit...") will be more clear.

Messages should describe general rules, not specific objects, because the main goal is to teach the user the rules. For example, write "the author", not the specific author's name.