accountDataAsTsv = account =>
  ACCOUNT_DATA_FIELDS.map(key =>
    key === 'emailAddress' ? '' : account[key].toString()
  ).join('\t')
Formats an account object as a string of tab-separated values.

Note that no escaping is required, since all fields consist of
non-whitespace characters in the printable subset of Unicode. See [1] for
username constraints.

[1]: https://docs.aws.amazon.com/cognito-user-identity-pools/latest/APIReference/API_UserType.html