Use the gradesReleased attribute for AGS line items to control when grades are shown in the platform.

[christianp]

Blackboard Ultra supports (and has designed?) the attribute gradesReleased on line item objects. We can use this to tell the platform whether scores that we have reported should be shown to the students.

This will require adding support for gradesReleased to pylti1p3 - it's just a boolean - and for the Numbas LTI tool to set it appropriately.

At the moment we assume that the consumer will take charge of releasing grades, so we might need a setting for "date to release scores", or a button to do it, or it should follow the "when to show scores to students" and "when to report scores back" settings. Since reporting incomplete scores is now possible, maybe "when to report scores" should be folded into "when to show scores" and the options should be:

• always (gradesReleased: true)
• when attempt is complete (gradesReleased: true)
• when review is allowed (gradesReleased is set to true when the review date passes)
• when instructor releases them (there'd be a button on the dashboard, which sets gradesReleased to true)
• never