Output error infromation with the database name
Don't merge nil and other type object
Allow to merge two hashes
Merge hashes simply for "sum" reducer
Define error status codes as constants
Make output messages' "errors" and "status code" changable
Output error status code for the collector
Export "errors" in the body to the envelope
Collect status codes from errors correctly
Return first error as the body
Extract error body correctly
Return all errors as a part of the envelope