/usr/lib/ghc-doc/hoogle/libghc-happstack-authenticate-doc.txt is in libghc-happstack-authenticate-doc 2.3.2-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-happstack-authenticate-doc/html/happstack-authenticate.txt