Django-cache-headers

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. Django 2.0 and Python 3 compatibility. Django 1.9 support has been dropped.

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. Fix anonymous-only policy to consider isauthenticated cookie.

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. Ensure isauthenticated cookie expires at end of session if session is set to do so.

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. An anonymous user may in fact have a session. Handle this case gracefully.

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. Added vcl generation management command, to be used in tandem with varnish. sample.vcl updated to reflect usage.
. Make use of on_user_auth_event to ensure no-cache header is set during login and logout.
. Extra protection against tampered session cookie.
. Policies no longer makes an assumption on the session cookie name.

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. Iterate over regexes in order of most specific (longest) to least specific (shortest).
. Revert OrderedDict change since it is not required anymore due to the above change.