docs: [FC-0002] plugin extensions ADR

[GlugovGrGlib]

In this ADR you will find a proposal to adopt plugin extensions system, initially implemented in the Open edX platform, but latter was extracted from it and now is ready for using by IDAs, ref. https://github.com/openedx/edx-django-utils/blob/master/docs/decisions/0002-extract-plugins-infrastructure-from-edx-platform.rst.

This ADR is proposed as a part of FC-0002 General Design for Sharing Open edX Credentials

Ticket: https://github.com/openedx/credentials/issues/1735

[openedx-webhooks]

Thanks for the pull request, @GlugovGrGlib! Please note that it may take us up to several weeks or months to complete a review and merge your PR.

Feel free to add as much of the following information to the ticket as you can:

• supporting documentation
• Open edX discussion forum threads
• timeline information ("this must be merged by XX date", and why that is)
• partner information ("this is a course on edx.org")
• any other information that can help Product understand the context for the PR

All technical communication about the code itself will be done via the GitHub pull request interface. As a reminder, our process documentation is here.

Please let us know once your PR is ready for our review and all tests are green.

[e0d]

@GlugovGrGlib Thanks for this ADR, the references are very helpful, the decision seems well aligned with our other document architectural decisions. Broadly I approve of this direction, though I haven't officially approved the PR as I think it's critical that that is done by the maintaining team.

[e0d]

@cdeery @GlugovGrGlib cannot merge this, would you do the honors?

[openedx-webhooks]

@GlugovGrGlib 🎉 Your pull request was merged! Please take a moment to answer a two question survey so we can improve your experience in the future.