proof
Calls the issuer to start proofing the applicant.
This will fail unless the state returned by getState is in the condition DocumentCondition.PROOFING_REQUIRED.
If this completes successfully, the condition will transition to DocumentCondition.PROOFING_PROCESSING
Return
a Proofing instance.
Parameters
documentId
the document to perform proofing for.
Throws
if not in state DocumentCondition.PROOFING_REQUIRED.
UnknownDocumentException
if the given documentId isn't valid.