I have had to send an email to supportapis-help@cisco.com to grant me access to the BUG v2.0 and v3.0 APIs, add those APIs to my Web App and then was able to query the URLs given in the docu. Give them your CCO ID in the mail as well! 

Hey Anthony, a colleague of mine gave me a hint and let me know that I might have overseen the key fact in my specific case: we haven't entered FQDNs in the LDAP config and that will lead to TLS verification not working.So, maybe the COP file would h...

Hey, just in case some other poor soul stumbles on this issue and finds this thread... There's a COP file for CUCM 11.x that has "ldap_ssl" (edit: Anthony has posted the title below) in the title, which hasn't fixed the issue for us but TAC recommend...