feat: add error level flag #657

[danh91]

@jacobshilitz

Is your feature request related to a problem? Please describe.
Some carriers return notes and warnings which are not errors, but they can be useful.
for example, FedEx we disabled the "note" type messages because it was not an error, see commit 4d2a07b.

Describe the solution you'd like
Add a level to message object that indicates whether it's an error or just a notice.
and add support for all the carriers

I thought it can maybe also be a setting in the user or in the API in each call, what errors should be suppressed