chore: [SIW-1684] Expose iat and exp claims

[gispada]

List of Changes

• verifyAndParseCredential returns iat and exp claims as issuedAt and expiration respectively

Motivation and Context

We need to know the expiration and issuance date of credentials. The exp claim is included in the JWT payload, the iat is found among disclosures.

This PR attempts to expose those claims in a simple and backward-compatible way, adding them to the object returned by verifyAndParseCredential. Since this function is always called at the end of the issuance flow, it is convenient to also get some additional metadata without requiring another step of verification/decode later.

The use of includeUndefinedAttributes was discarded to avoid getting claims not declared in the issuer configuration.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[LazyAfternoons]

LGTM