Helpers do not have all properties

[lopenchi]

Issue Summary

Checking the request body for mail/send (https://docs.sendgrid.com/api-reference/mail-send/mail-send), it was discovered that helper classes provided in this library are old and do not contain all info needed.

Errors found:

• In mail object, there are some properties that are not in Mail helper class: reply_to_list

• In MailSettings helper class there is a property bcc that it is not described anymore in the request body

[JenniferMah]

This issue has been added to our internal backlog to be prioritized. Pull requests and +1s on the issue summary will help it move up the backlog.

[Ravis22]

I also need this feature where I can set multiple reply_to