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_settings object, there are some properties that are not in MailSettings helper class: bypass_spam_management, bypass_bounce_management and bypass_unsubscribe_management

• 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.

[arkitex]

@JenniferMah hi folks - added a PR to address the first point: #707