New endpoint for creating verifiable credentials

Currently the service offers endpoints for creating VP or generating proofs on VC/VP, but not for creating VC.

This task will include a few additional sub-tasks:

• New HTTP endpoint for generating VC from random JSON (credentialSubject)
• Support the creation of multiple proofs (signatures) on a VC
• Support verification of multiple proofs of a VC
• Update integration tests to include cases for new functionalities
• Update healthcheck endpoints to include service version