Provide an LDAP Directory that is more resilient to bad network and bad LDAP

Context

Some clients have a crappy LDAP and/or crappy network so they have authentication issues when Nuxeo is trying to do LDAP operation.

Since this is a recurring problem, even if this is not really a Nuxeo issue, we probably have to work on finding a workaround.

Approach

To do that we would have a new kind of mixed LDAP/SQL directory that :

• tries first to authenticated against LDAP
• store (cache) the result in a SQL DB
• catch errors and falls back to SQL data if LDAP access fails

The idea is basically to :

• replicate progressively the LDAP inside a store that is managed by Nuxeo
• provide transparent fall-back