[Task] Support publicKeyJwk verification material format

[cycraig]

Description

Implement publicKeyJwk as a verification material format according to the DID-core specification.

We currently have a placeholder enum for publicKeyJwk that is not implemented.

Motivation

Comply with the W3C DID specification.

Resources

• W3C DID-core specification
• Combined compliance tracking issue [Task] Implement JSON-LD output format for DID Documents #196

To-do list

Create a task-specific to-do list . Please link PRs that match the To-do list item behind the item after it has been submitted.

• Implement publicKeyJwk, with tests
• Add publicKeyJwk examples with various combinations of valid properties in the JWK

Change checklist

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• The feature or fix is implemented in Rust and across all bindings whereas possible.
• The feature or fix has sufficient testing coverage
• All tests and examples build and run locally as expected
• Every piece of code has been document according to the documentation guidelines.
• If conceptual documentation (mdbook) and examples highlighting the feature exist, they are properly updated.
• If the feature is not currently documented, a documentation task Issue has been opened to address this.

[l1h3r]

This will need one or more signature suites before it can be fully utilized in a DID Document. Currently there is the JSON Web Signature 2020 suite from the Linked Data Proofs spec but it uses a JSON-LD canonicalization algorithm that we didn't intend to support (JSON-LD support is a much bigger task).

I added this issue for creating a new suite with a supported canonicalization algorithm. It can be picked up anytime by anyone and will probably need a bit of discussion regarding supported algorithms though.