Make %+v formatting of ErrorFormatter optional

[cyphar]

Not all users want, by default, to have their pkg/error errors' stack traces printed. This should be handled by a --debug flag or Debug option in the App, so that you only get a stack trace if the user actually asked for one.

[jszwedko]

👍 I can definitely see that argument, apologies for not conceiving of it when reviewing #560.

I'll mark this as a bug.

[coilysiren]

Given that this is from last year, I think I'm comfortable closing it 🙂 feel free to re-open / open a new issue / comment in support if there's still interest here!