Allow JWT Token to be retrieved even if user isn't logged in

Allow a JWT token to be retrieved from /api/v2/help_center/integration/token even if you're not logged in. Then that token could be sent to the third party service which could verify it. Of course, the third party service couldn't verify the user, but at least it could verify the source of the call, ie that the call came from zendesk.

As for our use case, we use a third party service that provides additional functionality to our zendesk helpcenter pages, ie categories, sections and articles. We don't force users to log into our site so much of the time, this service is being called anonymously.

For more context on this JWT token feature: https://support.zendesk.com/hc/en-us/articles/5860358664730-Announcing-Secure-end-user-experience-integrations-for-Help-center#comment_5943682644890