[feature proposal] Support for Openproject

Openproject (https://www.openproject.org) is an open project management system that tracks the evolution of "work packages", a work package can be a bug, a task, a user story or other kinds but in essence the work packages are activities that needs to be done and might have an assignee and an "accountable user".

Project is free and API is documented here https://www.openproject.org/docs/api/introduction/ and via an openapi/swagger behind login.

Openproject can be selfhosted or used in cloud.

I'm not a heavy user of openproject (yet) but it would be a nice source to be able to pull tasks from