Delegate VC/VP verification to the signer

Motivation

Currently, infohub asks the signer to produce VC/VP proofs when needed, but when data has to imported, the infohub verifies the incoming proofs of VC/VP by itself. To unify and better separate the concerns of each service, make proofs verification use the signer service too.

For this to be possible, first signer#14 (closed) must be completed and then the infohub service must be changed to use the new endpoints for proofs verification.