Improve breadcrumb data serialization and handling of ServerError.result

[spawnia]

Resolves #278

The first part towards solving this issue is recognizing when a thrown error includes a result. I think the correct thing to do in that case is to respect the value of the includeFetchResult configuration and act accordingly.

The second part would be to do deep serialization of certain parts of the breadcrumb. I am not quite sure how that is best handled, especially when considering attachBreadcrumbs.transform - this function expects a breadcrumb that still holds structured data, that should be the most useful to work with. Should we just JSON-stringify every key of the transformed breadcrumb afterwards?

[spawnia]

@alesso-x @DiederikvandenB

[alesso-x]

Should we just JSON-stringify every key of the transformed breadcrumb afterwards?

I think this makes sense, as user I don't have to worry about transforming the data myself.

[mic-web]

Should we just JSON-stringify every key of the transformed breadcrumb afterwards?

I think this makes sense, as user I don't have to worry about transforming the data myself.

Yes I think that makes sense for the default behavior and for the most usage scenarios. In some rare cases it might also be helpful to have the option of passing a replacer function (which could be forwarded to JSON.stringify):
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify#the_replacer_parameter

[DiederikvandenB]

Thanks @spawnia. I'll merge & release.