Use LDAP to retrieve user name
When user are only present on LDAP and not on the system, slurm-web failed silently on login because it can't retrieve the user name (parsing of gecos using pwd python library).
I patched the function to firstly look at the LDAP 'givenName' field of a given user. It still use the old function if it can't retrieve the name through LDAP or if he got an error.
This pull request concerns Slurm-web v2 which is not maintained anymore. You are highly encouraged to test the new version v3.0.0 that is officially maintained. The quick start guide for v3.0.0 is available online: https://docs.rackslab.io/slurm-web/install/quickstart.html
Unless someone is motivated to maintain the old version of Slurm-web or you have a justified reason to keep this pull request open, it will be closed in a few weeks.
For the reasons explained in the previous comment, I finally close this PR.