Add “preposttest” mastery model constant and update schema for pre/post assessments

[LianaHarris360]

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Description

To support the new Course -> Unit -> Pre-test -> Lesson(s) -> Post-test structure, we need a new mastery-model variant that explicitly supports A/B versions of pre and post tests attached to a single Unit. The existing MASTERY_MODELS should be updated to allow two distinct versions (A vs B) of one assessment set, which will be used for an accurate comparison of test results at the start and end of a Unit.

Outcomes

• Add a new constant within le_utils/constants/exercises.py for a preposttest mastery_model type:
  • MASTERY_MODEL.PREPOSTTEST = "preposttest"
• Update le_utils/spec/schema-mastery_criteria.json:
  • Add "preposttest" as a possible value in the "mastery_model" enum
  • Under "definitions”, define a new schema "preposttest" and include the required fields:
    • assessment_item_ids: array of all item IDs (both A and B)
    • version_a_item_ids: array of item IDs for version A
    • version_b_item_ids: array of item IDs for version B
  • Update the "anyOf" array so that when mastery_model == "preposttest", the object must include the three new required fields.
• Ensure current schema tests pass and add test schema validations for the new "preposttest" type to confirm valid and invalid cases.

[akolson]

@LianaHarris360 are the assessment_item_ids, version_a_item_ids, and version_b_item_ids uuids? If so, would it make sense to validate the uuids ids too? cc @rtibbles

[rtibbles]

Yes, they should all be uuids (either v4 or v5, depending on whether they were created via ricecooker or Studio).