Adapter: ResponseStatusException message is not present in response body

[sonallux]

The message of a ResponseStatusException is not added to the HTTP response body. I would expect the exception message to be present in the response body for easier debugging and error spotting.

Reproducible example

When adding a new Datasource (PUT /api/adapter/datasources) with an id already specified, the response does not contain the error message of the thrown ResponseStatusException from this line: https://github.com/jvalue/open-data-service/blob/8404c3761ac5f46cfbe3367253e2f61916eff3ea/adapter/src/main/java/org/jvalue/ods/adapterservice/datasource/api/rest/v1/DatasourceEndpoint.java#L43 Instead the response body just contains this:

{
    "timestamp": "2020-10-28T17:27:40.435+00:00",
    "status": 400,
    "error": "Bad Request",
    "message": "",
    "path": "/datasources"
}

[sonallux]

Closed by #322