Log response body on error

[gjedlicska]

Whenever we return a 4** or 5** status code from the server, we should include the response body with the log message. It helps a lot with diagnosing issues.

[iainsproat]

The response body may contain tokens or GDPR related material (e.g. email), which we would not want persisted in logs. Do we just wish a particular path to be logged if it exists, e.g. .error_message or similar?