Add support for verifiable credentials

[ahmed-arb]

Verifiable credentials are supported by the credentials service. The following presentation and documentation have a more in-depth context:
https://www.youtube.com/watch?v=HQ7e0OQQEBE
https://docs.openedx.org/projects/edx-credentials/en/latest/verifiable_credentials/overview.html

Additionally, this plugin by racoongang sets up the required configurations:
https://github.com/raccoongang/tutor-contrib-badges

[ahmed-arb]

Apart from following the steps in the official docs, we need to add an entry in the "Credentials api configs" table in lms admin and check the "Enable Learner Issuance" flag.

[ahmed-arb]

Created a PR to add Wikimedia's testing issuer.
digitalcredentials/sandbox-registry#26

[ahmed-arb]

Discussion post for bugs credentials and LCW bug: https://discuss.openedx.org/t/verifiable-credentials-qr-code-scan-issue-stuck-at-credential-storage-step/18349/6