Allow users to associate Videos with Lessons

[ColeDCrawford]

Related to #87 - linking ES content to Django content.

[lukehollis]

Hi @ColeDCrawford and @rsinghal following up from email "Could you all describe how you want the data model and relationships to be laid out now?"

[ColeDCrawford]

You can currently associate Topics and Collections with a Lesson. @npicardo can chime in here, but I think we just want to also be able to associate Videos with Lessons. That would require a new field to store the videos, an update so that the Django admin page displays the field, and then displaying the correct data on the end user side #92 .

Again, the field should probably have a picker that would hit Elasticsearch with a filter for item type = video, but the bare minimum is just a list of IDs. In this case you know what the item type is (all videos) so you wouldn't run into the same disambiguation problems as items in Collections.

[npicardo]

Ultimately we need each individual Lesson Topic page to display a designated selection of videos that users can launch from there (i.e. as part of the lessons' content resources). As content on the page, videos selected for an individual Lesson Topic will not change frequently, so they can be hard-coded into the page if that's a viable path of least resistance. All of them are in TMS already, if that's helpful to know.

[lukehollis]

From @npicardo: "The attached spreadsheet has the two different kinds of links, plus a caption/title for each video if that’s possible, to give users an idea of the content of each." Giza@School Lesson Topic Videos-updated.xlsx Should appear like this: