Consistent error handling

- [x] Server must return errors that have consistent format.
- [x] Unify way of handling with Throw and Callback errors.
- [x] Handle all errors. Now app can skip some errors, for example in PulsarDB.
But I think it's good practice to always implement this err-ready callback. I think that's what you expect from usage. Addiitonally if will change way this works it might actually throw error and then we need to refactor all usages.