Configure LTI Advantage Assignment and Grade Services (AGS) to create a line item programmatically and post scores without a preceding student launch

Steps

1. Obtain a service access token scoped to https://purl.imsglobal.org/spec/lti-ags/scope/lineitem and https://purl.imsglobal.org/spec/lti-ags/scope/score by POSTing a signed JWT client assertion to the platform's token endpoint.
2. To create a new line item, POST to the lineitems endpoint URL (from the launch JWT claim or stored deployment config) with a JSON body containing label, scoreMaximum, resourceId, and tag fields; the platform returns the created line item including its id URL.
3. To post a score for a specific student, POST to <lineitem_id>/scores with Content-Type: application/vnd.ims.lis.v1.score+json; the body must include userId (student sub), scoreGiven, scoreMaximum, activityProgress, gradingProgress, and timestamp.
4. Set activityProgress to 'Completed' and gradingProgress to 'FullyGraded' to signal a final grade; use 'PendingManual' when the score requires instructor review.
5. To read back scores, GET <lineitem_id>/results with the scope https://purl.imsglobal.org/spec/lti-ags/scope/result.readonly; results are paginated using Link headers.
6. When the platform pre-creates a line item (resourceLinkId bound), retrieve it via GET /lineitems?resource_link_id=<resourceLinkId> rather than creating a duplicate.