[Suggestion] Rename 'Check Source' to 'Command Endpoint'

[junglistikal]

To be more consistent with the Icinga2 API, can 'Check Source' be renamed to 'Command Endpoint'. It would add a little less confusion to newcomers of Icingaweb2 who are creating their checks via API.

[dnsmichi]

check_source is not necessarily the command endpoint. It may also originate from the local scheduler on this instance.

Also, check_source is the key provided by Icinga 2's API when querying for check results.

[nilmerg]

The term endpoint has a specific meaning while check source is more of a general term. And since Icinga/icinga2#2985 check_source gets the endpoint's name by default. (Implying that it may not be the command endpoint)

So I'd say we keep things as they are.