3709: LDAP periodic sync of user / group information to make sure info is up to date

When reviewboard is connected to LDAP, upon login, the user information (username, email, etc) is captured and stored in reviewboard. Over time this information can get out of sync if LDAP is updated. I do not believe this information stored in reviewboard gets updated until the user logs in again, if ever.

Take this example:
- User exists, review created, added to groups, etc.
- User is disabled in LDAP, email address changed, etc.
- The review that a user is a member of is updated, thus an email will be sent out to the user.
- Since reviewboard works off of the user information in its database, it may be sending emails to incorrect addresses, for users that have been disabled, etc.

Since reviewboard needs to cache user information for its work, it should periodically sync with LDAP to make sure that its information is up to date / correct. At the moment, we have to manually update the reviewboard information when we disabled users in LDAP, etc. This greatly increases the maintenance effort required, making it difficult to scale to a large user base.

Review Board version: 2.0.11
Authentication: LDAP

#1 msunde
This is a superset of issue #1876