CoseMac0 Support

[alex-richards]

What is the areas you would like to add the new feature to?

Go-COSE Library

Is your feature request related to a problem?

No support for CoseMac0.

What solution do you propose?

Adding support.

What alternatives have you considered?

NA

Any additional context?

No response

[SteveLasker]

see #86
Happy to have Mac0 support, if someone is willing to initiate a PR.

[alex-richards]

@SteveLasker I'm currently working on it.

Copying the basic structure of Signature and Sign1. Should have PR in a few days, assuming life doesn't get in the way.

[Juanmalopezg]

Hi @alex-richards , thanks for working on this 🙌🏼
I locally tested #198 and it looks good to me. Do you think you could rebase it on main now that #205 has been merged?
Also, are you planning to implement support for COSE_Mac0 (tag 17) in the same PR?

[alex-richards]

Hey @Juanmalopezg,

Yeah, the original plan was to do COSE_Mac0 too, but I'm pretty low on free time at the moment, so it might be best to get this done and come back to Mac0 later.

There are a few tests to complete to bring it up to parity with COSE_Sign and some TODOs that I don't have an answer for. I'll rebase this and add GH comments where I need input.

Cheers, Alex