Add storage engine for Microsoft OneDrive

[burck1]

Here's my attempt to add Microsoft OneDrive support.

OneDrive on macOS; why would you do such a thing?!? It's not by choice; my employer is an Office365 shop and they make us use OneDrive on the macOS dev machines...

Example Configuration

[storage]
engine = microsoft_onedrive

Referenced Issues

• Microsoft OneDrive #1049

All submissions

• I have followed the Contributing Guidelines
• I have checked to ensure there aren't other open Pull Requests for the same update/change

Adding/updating storage engine support

• This PR is only for one storage engine
• It has been added to the list of supported storage engines in the README
• Changes have been added to the WIP section of the CHANGELOG
• Syncing does not break the application
• Syncing does not compete with any syncing functionality internal to the application
• The configuration syncs the minimal set of data
• No file specific to the local workstation is synced
• No sensitive data is synced

Improving the Mackup codebase

• My submission passes the tests
• I have linted the code locally prior to submission
• I have written new tests as applicable
• I have added an explanation of what the changes do