docs: ADR introducing mobile offline content support

[GlugovGrGlib]

Description

This is draft ADR that describes offline content generation to make it available on mobile.

Supporting information

FC-0047 (link TBD)

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[angonz]

I suggest adding a comprehensive list of content types that will support offline viewing (maybe not all will be implemented at a time).
I think that video content deserves special attention. Many courses rely on video content. Open edX usually relies on external streaming services for video (YouTube, Vimeo, etc.) Video files can be huge. How will it handle offload video? Maybe uploading a downloadable version of the video in a separate storage?
Another thing to consider is milestones. If grading cannot be done offline, then probably unlocking content based on subsection grade will not be possible.

[salman2013]

@GlugovGrGlib Just for curiosity how this ADR is different from this PR?

[NiedielnitsevIvan]

I suggest adding a comprehensive list of content types that will support offline viewing (maybe not all will be implemented at a time).
I think that video content deserves special attention. Many courses rely on video content. Open edX usually relies on external streaming services for video (YouTube, Vimeo, etc.) Video files can be huge. How will it handle offload video? Maybe uploading a downloadable version of the video in a separate storage?
Another thing to consider is milestones. If grading cannot be done offline, then probably unlocking content based on subsection grade will not be possible.

Hello @angonz! I have updated the ADR and now there is a list of blocks that are planned to be supported. I also added a diagram to make it clearer how the content generation process will work. Please check it out.

As for videos, video uploading is already implemented in mobile applications.
As for unlocking content based on subsection grade, yes, such functionality is not planned within this work scope and, accordingly, it is not reflected in the ADR.

[NiedielnitsevIvan]

@GlugovGrGlib Just for curiosity how this ADR is different from this PR?

Hi @salman2013, the functionality added in the PR you mentioned corresponds to what is described in this ADR.
This ADR describes the overall vision, but focuses on how it is planned to be done on the backend.