Checkmk Werk 15216: rest_api: corrected the time period response schema

ID: 15216 Title: rest_api: corrected the time period response schema Component: REST API Level: 1 Class: Bug fix Version: 2.2.0i1 This werk introduces a fix for a bug that would cause a 500 internal error when fetching a timeperiod via the REST-API. This was caused when configuring sepecific days for activate_time_range in the GUI.