Add the ability to return a deep view of reference-repository

This allow to get a deep view of the reference api by passing the
`deep` GET parameters to the request.
It is also possible to request a single site or the specific list of nodes
assigned to an OAR job id.
3 jobs for features/#12051_deep in 21 minutes and 51 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Lint
passed #768772
grid5000-docker
rubocop

00:01:40

 
  Test
passed #768773
grid5000-docker
test-for-buster

00:10:01

86.66%
 
  Deb
passed #768774
grid5000-docker
deb-for-buster

00:10:10