Merge meta dictionary to root of body

[dgimb89]

Merging the meta dictionary on top-level of the body dictionary allows for more structural freedom of the constructed logs. That makes it easier to be consistent with existing projects that log to InsightOps and re-use saved queries across multiple log sets / projects.

In case of conflicts, the proposed implementation gives precendence to the body's values.

[ookami-kb]

Hi, your point is quite reasonable. However, I'm slightly confused about this assertion/removing keys – looks artificial.

I'm actually thinking about replacing getMeta parameter with something like transformBody with the following signature:

typedef BodyTransformer = Future<Map<String, dynamic>> Function(Map<String, dynamic>);

By default, it will just return the current body (created by the library), at the same time it will allow the client to fully customize the body, using it like this:

InsightOpsLogger(
  _url,
  transformBody: (body) async => {
    ...body,
    'meta': {'deviceId': 'ID'},
  },
);

What do you think, will it solve your use case?

[dgimb89]

That would definitely work for my use case. I didn't aim for a more generic approach like the one you suggested because I didn't want to change the interface. However, I like your solution better than the one I suggested in this PR.

The key removal makes sure we do not overwrite values defined by the body. The assertion was meant to help users of the package to detect collisions in debug mode without having to look up the fields defined for the body.

Happy to help with the implementation if needed.

[ookami-kb]

Cool! Resolved in #2