allow issuance of multiple cred at same revocation index

This PR proposes an option for the issuer to specify a cred_rev_id (index in revocation registry) when a credential is issued.This gives more control for an issuer to manage revocation registry, a few examples can be

Alice issues credentials with same cred_rev_id multiple times to Bob, who wants the same credential to be stored in multiple wallets, In this case Alice can revoke a credential of Bob by revoking a single index, this allows Alice to create a better controller logic for revocation registry
Alice issues credentials with same cred_rev_id to multiple Holders e.g. Coupons

@DaevMithran

Signed-off-by: Pritam Singh pkspritam16@gmail.com

hyperledger-archives / indy-sdk

allow issuance of multiple cred at same revocation index #2505