Add A `DeleteFile` and `Refresh` method to the interface.

[317jamtay317]

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Is the feature request related to a problem

The feature request is not a real big problem, but it would be nice to refresh the cachce programmatically, and clean up the stale files. From what I've seen the stale file are being stored and not cleaned up.

Describe the solution

Add a public DeleteFile and Refresh methods to the IHttpCache interface.

Describe alternatives considered

I have not tried this but I could potentially update the endpoint that is being refreshed manually as shown in the documentation.

Additional context

None.