add block timestamp to the issuer string of VC

[theblockstalk]

if somebody logs into an App, Signes a VC, Locked out and in again and then somebody tries to verify the VC it will fail because the key on the blockchain It is no longer the same key as the sign.

add block timestamp to the issuer string of VC So that it can be used to refer to a point in time in the bocce when the signing key existed on the account

Acceptance criteria

• When a VC is issued, fetch the account from the block chain and check that the public key used for signing is still there
• attach the block number to the issuer string e.g. ?blockNumber=1313268173
• Modify the antelope-did-resolver to 1st check the current state for the publicly and if that fails then, if there is a blockNumber query parameter to check the blockchain at that point in time