We automatically detect whether the server supports server side sorting
and sort manually if that is not the case. But there are LDAP servers
which report that they support this feature in general but have it
disabled for certain fields.
If we send the server side control for any field that has server side
sort disabled, the LDAP server will abort the query.
With the new configuration option it is possible to disable server side
sorting and it has precedence over our automatic detection.
Since this is a very special LDAP server configuration, there is no GUI
option for this.
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