error-reporting

Currently IntoDiagnostic wraps the Error that it is called on with a DiagnosticError.

https://github.com/zkat/miette/blob/e6f5cacfa65cfe26255a5686ceb610b4a211931b/src/eyreish/into_diagnostic.rs#L22-L26

This means that any further inspection using is or downcast{,_ref,_mut} will fail to reach the inner type and only DiagnosticError can be reached. Since it is an implementation detai

This case should just be passed directly to the parent handler

Currently we use protobuf to document the representation format: https://github.com/soundcloud/periskop/blob/master/representation/errors.proto.

Since we are not planning to use protobuf as a serialization format, it would be more appropriate to use json schema instead.

When creating exceptions with breadcrumbs in 2 tests, the second test will have the breadcrumbs from the first test.

describe('debug', () => {
    beforeEach(() => {
      testkit.reset();
    });
    it('should log a message 1', () => {
      Sentry.addBreadCrumb({message: 'messageText'});
      Sentry.captureException(new Error('test 1'));

      expect(testkit.reports()).toHaveLen