[2.3.0] Checkmk Werk 16508 created: Make LDAP connection test errors more explicit

[//]: # (werk v2) # Make LDAP connection test errors more explicit key | value ---------- | --- compatible | yes version | 2.3.0b3 date | 2024-03-07T16:34:41+00:00 level | 1 class | feature component | wato edition | cre The LDAP connection test does not give enough information about which DN configured results in an error. This werk adds identifying information for the DN to the error message to make it easier to identify the problem.