Apply grouping hash if method bugsnag_grouping_hash is available on the object

[Nowaker]

Conversion with Simon Maynard dated December 2015:

Proposal: what if you added support for passing a grouping hash through the exception object? If exception object that Bugsnag handler rescues respond_to? :bugsnag_grouping_hash, use this as the grouping hash.

You can get access to the exceptions by calling notification.exceptions and that should give that to you. I think adding grouping_hash support to exceptions would seem reasonable - we already have a similar thing for metadata in https://github.com/bugsnag/bugsnag-ruby/blob/master/lib/bugsnag/notification.rb#L313 and I'll look into doing that in the new year (unless you fancy sending a PR yourself). In the interim you could use the exceptions method https://github.com/bugsnag/bugsnag-ruby/blob/master/lib/bugsnag/notification.rb#L279

Thanks for pointing me to exceptions method. This will do the job. Ultimately, having grouping_hash (or bugsnag_grouping_hash?) would be the best. Very powerful with no plumbing needed.

When bugsnag_meta_data is available on an exception, Bugsnag adds it automatically to the Bugsnag report. So should be done with bugsnag_grouping_hash.