document the endpoint configuration option

Reported-by: Maxime Déraspe <maxime.deraspe.1@ulaval.ca>
Commit: 4f70801c9284063ea45d0bf609045e1f67dd98c6
Link: http://genome.ulaval.ca:10100/client
Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>