Checkmk Werk 15431: rule: Return a 404 when a rule doesn't exist on the GET endpoint

ID: 15431 Title: rule: Return a 404 when a rule doesn't exist on the GET endpoint Component: REST API Level: 1 Class: Bug fix Version: 2.3.0b1 This werk is to fix an issue with the GET rule endpoint. Previously the response contained a bug report when the rule didn't exist. Now we conform to our other endpoints and return a 404 problem response.