Delete member from project

[rosygupta]

Implement an API to delete a member from the project. Also, send notification to the deleted member via email.
Proposed Enhancement: Mark the deleted member and store this information. This would be useful in alerting the admin in case the member tries to gain access to the project in future.

[gedankenstuecke]

That API is now available through Open Humans' main site: https://www.openhumans.org/direct-sharing/oauth2-member-removal/

E.g. we can now implement this here too!