ErrInternal is an internal error that should be provided to the user (http api
will return a 500 with the error message)
It'll be used for any kind of error that are not auth or bad requests (like
errors to communicate to another service)
Don't create an ErrFromRemote wrapping the returned error but
wrap the ErrFromRemote
Also use xerrors Is/As to get the underlying error to return to api clients
while maintaining context for logging
* client: always parse the json error message field and return its contents
* Use ErrBadRequest and ErrNotFound in every handler and command
* Gateway: by default pass underlying service error (configstore, runservice) to
client keeping the status code and message. In future, if some errors must be
masked, we should change the specific parts that need special handling.
Simone Gotti