Add extensible course view types for edX platform

[andy-armstrong]

This is the first step to supporting pluggable features in the edX platform. A new Stevedore "course_view_type" extension point is added, that allows any Django app to register a new view for the course. Currently, each course view is shown as a tab in the course, but a client is free to choose whether these are shown as tabs. In particular, on mobile there UX may not be represented as tabs.

To prove out this change, the following tabs have been converted to course views:

• the "Notes" tab provided by Student Notes
• the "CCX" tab for CCX administration
• the "Instructor" tab that shows the dashboard

See this wiki page for the background:

https://openedx.atlassian.net/wiki/display/AC/Feature+Plug-Ins+for+edX+Platform

[andy-armstrong]

Note: this work has been separated out from https://github.com/edx/edx-platform/pull/7937 where it was originally implemented.

[andy-armstrong]

@cahrens @cpennington please review this newly separated out PR to provide extensible tabs.

FYI: @antoviaque @bradenmacdonald @ormsbee @dan-f @dianakhuang

[andy-armstrong]

@nasthagiri We should chat sometime soon about how this extension point (and future ones) can play nicely with mobile.

[andy-armstrong]

FYI, the build failure is now down to quality issues. I plan on addressing these later today.

[dianakhuang]

We already talked about this, but at least for this feature, it doesn't seem necessary to have a separate class for this.

[andy-armstrong]

As we discussed, it seems simpler to have the plugin's define their own name field, rather than have this complicated logic to wrap each plugin. Unfortunately there's an instanceof check that I need to remove, but that should be fine.

[andy-armstrong]

@dianakhuang @cpennington I've generalized the logic for how Studio dynamically adds tabs when features are enabled. This should now work for the "Teams" tab which needs to enable itself based upon something other than the existence of a boolean feature flag.

edx@cbe5e18

[dianakhuang]

test this please

[cpennington]

What API does a Feature have to implement?

[dianakhuang]

I imagine that Feature is going to get fleshed out a bit more later when we start implementing teams using it. I can take it out of this PR if it's too distracting.

[andy-armstrong]

This was my mistake. I intended to remove it when I implemented tabs as a first-class extension point. @dianakhuang please go ahead and take it out.

[dianakhuang]

After doing a quick spot-check on devstack, the Instructor tab is not showing up in the LMS. I'm going to investigate.

[dianakhuang]

Huh, maybe I didn't reinstall/run setup.py or something like that, but it seems to be working fine right now.

[cpennington]

{p['type]': p for p in [OPEN_ENDED_PANEL, NOTES_PANEL]}

[cpennington]

Done w/ my review pass.

[dianakhuang]

Thanks @cpennington ! I'll get on fixing these.

[cpennington]

Nit: it looks like there's a lot of duplicated code in PUT vs POST. Is it worth abstracting, perhaps by using a class-based view?

[cpennington]

Done with this review pass.

[dianakhuang]

FYI @cpennington I had a commit specifically for addressing your feedback, if you wanted to review that before giving us a thumbs up on this PR.

[cpennington]

👍

[dianakhuang]

The one failing test is flaky. On rerun, it passed: https://build.testeng.edx.org/job/edx-platform-specific-tests/84/