Contentbody convert API returns successful response codes when the conversion results in an error

Issue Summary

The contentbody convert API (/wiki/rest/api/contentbody/convert/{to}) returns successful response codes when the conversion results in an error.

Steps to Reproduce

1. Invoke the API as follows:
   1. To format: view
   2. From format: storage
   3. From content: <p>a href="https://foo.com">bar</a></p>
2. Observe the response.

Expected Results

The returned JSON includes a field identifying the conversion was unsuccessful.

Actual Results

The response code is 200 and the returned JSON does not include any field identifying the conversion was unsuccessful. The only indication is the error message in the field that is used to return the converted content.

Workaround

None