Implement preferred LDAP for each user and auth against it

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 6.1.1 CE GA2, 6.1.20 EE GA2
• Fix Version/s: 6.2.0 CE M2, 6.2.0 CE GA1
• Component/s: Application Security > LDAP, Application Security > Login/Sign in Portlet, Portal Services, Security Vulnerability
• Labels: None
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/7595

Multiple LDAPs could be defined to support the authentication. When user comes, iteration over all LDAPs is performed, till the first success is found. With multiple (slow) LDAPs this could be a time consuming task and could make the Sign Up process significantly longer.

Since most users stay in the same LDAP, it would be nice to remember the latest used LDAP for each user and use it preferrably with the next Sign In attempt to speed it up. As a fallback, the iteration could be used it preferred LDAP fails. Preferred LDAP could be used only if user's account is already present in Liferay (was inported from LDAP before).