Creates a link that opens a completed envelope online (documents, signers and certificate) for anyone holding it, even after the access policy has closed the envelope to the link printed on the document. Several links can live at once; each has its own validity (one of the validityDays of the list endpoint), an optional label and an optional password. The URL with its secret is returned only in this response. The envelope must be final (signed, rejected, cancelled or expired) and the account needs a paid plan.