Checkmk Werk 12350: API: addition of get single downtime endpoint

ID: 12350 Title: API: addition of get single downtime endpoint Component: Core & setup Level: 1 Class: New feature Version: 2.1.0i1 This werk adds the get single downtime endpoint. It was already possible to get a single downtime using the query functionality in the show all downtimes endpoint. The new endpoint offers a more simple alternative.