fix(data-store): support credentials with undefined `issuanceDate`

[mirceanis]

What is being changed

BREAKING CHANGE: this changes the NULL constraints in the claim and credential table for the issuanceDate column, requiring a migration. A migration has been added to the default migration set provided by Veramo, but it is otherwise a breaking change if you are not using that set.

Quality

Check all that apply:

• [X] I want these changes to be integrated
• [X] I successfully ran pnpm i, pnpm build, pnpm test, pnpm test:browser locally.
• [X] I allow my PR to be updated by the reviewers (to speed up the review process).
• [ ] I added unit tests.
• [X] I added integration tests.

Details

I'm not sure we should be accepting VCs that don't (adhere to the data model](https://www.w3.org/TR/vc-data-model/#issuance-date). I'm posting this here as a continuation of #1273

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.