Icingaweb2: Allow to configure a client_cn for Icinga 2 API command transport

[Darkentik]

I found this old but closed issue https://github.com/Icinga/icingaweb2/issues/2541, that forwards me to this issue https://github.com/Icinga/icingaweb2/issues/3036 which was closed with "won't fix". So it seems that there is now no solution to use a cert parameter in Icingaweb2 for commandtransports.ini and i have to use basic auth. Sry if i missunderstand something in the mentioned issues. Maybe @dnsmichi or @Al2Klimov can say something on this, because you guys were working on this in the past. Thanks a lot!

Is your feature request related to a problem? Please describe.

I cannot configure a client certificate in the monitoring module for commandtransports.ini.

Describe the solution you'd like

We just need a config parameter for this like you configure in Icinga2 api.users.conf

[dasJ]

Proof of concept: #4587