There are circumstances when having a built-in authentication scheme is not practical. For these we should enable a wiki site to be wrapped in a layer that protects the site.
We acknowledge that we will never be able to provide support for every possible authentication scheme, or integration with corporate security solutions. So, we foresee that it will be necessary to accept the user's identity from an outer security layer.
This layered approach will be provided by the use of a proxy, that handles all wiki requests ensuring that only authorized requests reach the wiki server.
While how to deploy this outer layer is outside our scope. But, a Modular Authentication plugin should be provided to demonstrate picking up the user's identity from this outer layer.