Support for automated removal of single downtimes

[K0nne]

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

Hello!

our users are using the icingaweb2 api in different automated workflows. They need a way to remove downtimes for individulal services.
Is there a way to add this?

Describe the solution you'd like

/icingaweb2/icingadb/downtimes/delete?service.name=<hostname>!<servicename>

Describe alternatives you've considered

The usage of /icingaweb2/icingadb/downtimes/delete?host.name=<hostname> to remove them all is in some cases too much on an sledgehammer approach, where users need to remove only selected downtimes.

[nilmerg]

#1059 ?

[K0nne]

I am completely blind. I thought the other issue had already been merged, so I createt a new one -.-