Generate certificate when all enrollment are passed

[jbpenrath]

Feature Request

Is your feature request related to a problem or unsupported use case? Please describe.
Joanie must be able to generate a certificate when a product contains one. But certificate delivery should be trigger only when the the student has passed all related graded enrollments.

Describe the solution you'd like

Feature

First we should add a BooleanField is_graded to the CourseProductRelation table to be able to take in account only some courses of a product for progression.

Then we should add a field to register the student progression to the enrollment model. An enrollment should passed, not_passed or None if user has not yet try to pass the course.

Once we have these two information, we are able to know when a student has passed all graded courses to deliver its certificate.

API

/api/certificates : a route to retrieve all certificates for a user
/api/certificates/:certificate_uid/download : a route to request the certificate document in PDF format.

Do you want to work on it through a Pull Request?
Yes

[sampaccoud]

Should we record it in Joanie's db (and get synchronization issues as it is not really the source of truth?) or can we afford to query the LMS each time we need it (with some cache if necessary?)

[jbpenrath]

Hmmm... that's sound good to keep LMS as the only source of truth. But currently, we should request the enrollment state when we retrieve user orders and this is something did regularly.

If we decide to request LMS to retrieve enrollment state, we have to build a good logic to avoid spamming :

1. As you suggest we should cache the result (lifetime: 24h?)
2. We should only request state for enrollment related to course run opened
3. We should not request enrollment state if the certificate has been generated
4. Maybe the route to retrieve enrollment state from LMS should return all users's enrollments at once ?

On the other hand, I think this logic does not scale well when we will plug Joanie with several LMS.

[sampaccoud]

not 24h for sure... maybe 10 minutes max 😅 but anyway if you save it in joanie's db you will also not be in sync... Or maybe, since you are adding an endpoint in fonzie, OpenEdX can call the course run hook when something changes in the grade?

[jbpenrath]

Closed by #86