Checkmk Werk 15600: group_config: return the correct collection response for host/service/contact_group endpoints

ID: 15600 Title: group_config: return the correct collection response for host/service/contact_group endpoints Component: REST API Level: 1 Class: Bug fix Version: 2.3.0b1 This werk introduces a fix to collection responses for host, service and contact group_config endpoints. For bulk-create and bulk-update calls, the link object in the responses did not align with the expected schema. Now we return the expected schema.