A RFC 4648 base64 string of the template CSV file to be validated. While 21 CFR Part 11 is enabled, every recipient needs a name: the CSV must carry a name column next to each placeholder email column (for example signer_name alongside signer_email), and each row must fill that name in wherever it carries the matching email, otherwise it returns a 422. A row that leaves both the email and the name blank sends nothing to that placeholder, so no name is needed there.