Modify GmailAPI to accept Multiple recipents of Emails

[Vincent-Ha]

As a developer, I want to give users many options when compiling an email. Currently, the Gmail API as is can only support one recipient of the email. We would need to add support for multiple users to send emails. We should also add the ability to CC people as well.

Tasks:

• Modify GmailAPI to allow sending emails to multiple people
• Add support for CC'ing people
• Add unit tests to confirm this implementation.

Done:

• Unit tests testing these functionalities run successfully.