React Native iOS does not report error causes (or multiple errors from an error array)

[getsaf]

Describe the bug

package: @bugsnag/react-native iOS does not report error causes (It works fine in Android).

Root cause is that the iOS event deserializer is hard-coded to only inspect/deserialize the first error that is reported https://github.com/bugsnag/bugsnag-js/blob/05588a1c7a58e538cf1763d81a2eeae59ac76124/packages/react-native/ios/BugsnagReactNative/BugsnagEventDeserializer.m#L48

Additionally, I found that the bugsnag-cocoa pod also hard-codes attachment of stack traces to the first error in the BugsnagEvent#errors array in the attachCustomStacktrace function which is also called in the event deserializer here (this makes it difficult to provide a full solution without also making changes to bugsnag-cocoa or duplicating some logic from bugsnag-cocoa into the bugsnag-js repo).

- (void)attachCustomStacktrace:(NSArray *)frames withType:(NSString *)type {
    BugsnagError *error = self.errors.firstObject;
    error.stacktrace = [BugsnagStacktrace stacktraceFromJson:frames].trace;
    error.typeString = type;
}

Steps to reproduce

1. Report an error with a cause property assigned
2. View the report in the Bugsnag web UI
3. See the cause is not reported

Environment

• Bugsnag version: 7.20.2
• Browser framework version (if any):
  • n/a
• Server framework version (if any):
  • n/a
• Device (e.g. iphonex):
  • Any iPhone device

Example code snippet

  const cause = new Error('This is the cause');
  const error = new Error('This is the error', {cause});
  bugsnag.notify(error);