[Task] Test functionality introduced in #1148 more thoroughly.

[olivereanderson]

Description

The JWT-based CredentialValidator in #1148 needs more tests. Currently the validate method has only been tested with the default options (in identity_storage) and most of the single purpose methods that have been ported from the old validator have not been tested at all.

I would suggest to:

1. Introduce some more unit tests in the module itself. Note that since it allows users to pass a custom JwsSignatureVerifier signature verification can easily be mocked and it will be easy to test all the other (composed) functionality.
2. Extensively test signature verification in identity_storage using the JwkStorageDocumentExt trait to produce signatures.
3. If official test vectors exist for the VC-JWT test suite it would be ideal to port those as well.

Furthermore it would also be good to test JwkStorageDocumentExt::sign_bytes and CoreDocument::verify_jws with more configuration options and make sure that the errors are also exercised in tests.

Motivation

The functionality we ship should be thoroughly tested.

Resources

Follow up task of #1148 and sub-task of #1103.

To-do list

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• Item one
• Item two
• Item three

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.