I've gone ahead and tried to make a custom connector.  A useful guide can be found here: https://gotoguy.blog/2017/12/17/access-microsoft-graph-api-using-custom-connector-in-powerapps-and-flows/

 

Nonetheless, I'm having a lot of trouble with authentication after making any changes to the Get call.  Also, it would be helpful to understand how to make sense of the Microsoft Graph documentation.  I'm trying to get calendar attachments by using GET https://outlook.office.com/api/beta/me/events/{event_id}/attachments but come up with different errors everytime.

 

All the best!