Add encoding option to specify how omitempty fields are encoded

[dinhxuanvu]

Description

The current behavior in the library is to omits if field value would encode as empty JSON value. This behavior is different from the bahavior in golang encoding/json which omits if field value is an empty Go value (defined as false, 0, a nil pointer, a nil interface value, and any empty array, slice, map, or string). The OmitEmptyMode = 1 is added to encoding option so that cbor would decode omitempty fields similarly to encoding/json in go.

PR Was Proposed and Welcomed in Currently Open Issue

• This PR was proposed and welcomed by maintainer(s) in issue feature: CBOR uses a different definition of "empty" than golang encoding/json for omitempty #445
• Closes or Updates Issue feature: CBOR uses a different definition of "empty" than golang encoding/json for omitempty #445

Checklist (for code PR only, ignore for docs PR)

• Include unit tests that cover the new code
• Pass all unit tests
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[fxamacker]

@dinhxuanvu Thanks for opening this PR! 👍

I left some feedback for your consideration and will try to include this PR in v2.6.0 if possible.

Thanks again!

[dinhxuanvu]

@fxamacker Thanks so much for the feedbacks. All are addressed! PTAL

[dinhxuanvu]

Force-pushed to fix a small fix with lint (variable name).

[fxamacker]

@dinhxuanvu Thanks for opening issue and contributing this PR! 👍

I'd like to include this in v2.6 and will take a closer look this weekend!

[fxamacker]

@dinhxuanvu Thanks for updating the PR! LGTM! 👍