If a feed requires credentials, OPDS Proxy can transparently
set them server side by reading the feed configuration.
This is useful in scenarios where the server operator sets up their
own authentication in front of OPDS Proxy and doesn't want to
have users remember separate credentials for each of the configured
feeds.
If keys aren't specified they will be generated. The downside
of this is that the keys will change every server restart
which will invalidate previously generated cookies.
If the keys are specified in the config.yml, they are
used between restarts and all previously generated
cookies remain valid.
Working *.epub to *.kepub.epub file conversions when
using a Kobo reader. Updated docker file to include
`kepubify` to convert to kepub. If not available the
file is just sent without conversion.
