Rename Credential struct fields

[iinuwa]

field names of credentialsd_common::model::Credential type are confusing/flipped: name is an ID/username, and username is a name. We should rename them (or just use the names from the WebAuthn spec).

[sejal2855]

Please assign me this issue

[iinuwa]

Hello @sejal2855! Thanks for the offer!

You can submit a PR whenever you're ready and we'll review.

By the way, we're working on a contributor guide, but it's not quite finished yet. I'll send you a link once it's finished.