Return the merchant email to RetrieveMerchant

[Graham]

The API used to return a business email with the merchant. It doesn’t anymore. It would be nice to not have to rely on the locations’ emails, since they aren’t required.

Note: There was no Merchant-API tag, so I added it to Oauth and the general SDK tags.

[Bryan-Square]

If you want to get the email of the account you can call SearchTeamMembers and parse the results for is_owner. That will give you the merchant account email.