static sanitizeString(str) {
    return str.replace(EQUAL_SIGN_REGEX, '=3D').replace(COMMA_SIGN_REGEX, '=2C')
  }
From https://tools.ietf.org/html/rfc5802#section-5.1

The characters ',' or '=' in usernames are sent as '=2C' and
'=3D' respectively.  If the server receives a username that
contains '=' not followed by either '2C' or '3D', then the
server MUST fail the authentication.

@returns {String}