fix(enrollment_detail_report): fix two join fan-out bugs

[rachellougee]

What are the relevant tickets?

NA
Discovered by #2469

Description (What does it do?)

Fixes bugs in enrollment_detail_report that caused duplicate rows (fan-out) for some enrollments, leading to inconsistent values after the switch to use dimensional models

• Course title: some enrollments show the wrong (outdated) course title instead of the course's current title.
• Coupon: some enrollments show a coupon name that belonged to a different platform's version of the same coupon code (e.g. an MITx Online enrollment showing an xPro coupon's name).

Also exposes enrollment_key as a new output column — a reliable unique identifier for each row, to help catch and track down any remaining duplicate-row issues

Test plan

• Verified both fixes by rebuilding the report from unchanged upstream data and confirming the previously-inconsistent values are now stable and correct
• Confirmed coupon names now correctly match their platform

How can this be tested?

dbt build --select enrollment_detail_report - a warning due to tfact_certificate's user_fk issues that will be addressed separately

Confirmed that coupon fields produce consistent values per platform

 select platform, coupon_code, coupon_name, count(*) as n                                                                                                       
  from "ol_data_lake_production"."ol_warehouse_production_rlougee_reporting".enrollment_detail_report                                                                    
  where coupon_code = 'NEWYEAR24'                                                                                                                                
  group by platform, coupon_code, coupon_name 

confirmed that course title shows the correct name for some courses

  select courserunenrollment_id, course_readable_id, course_title, courserun_readable_id                                                                         
  from "ol_data_lake_production"."ol_warehouse_production_rlougee_reporting".enrollment_detail_report                                                                    
  where course_readable_id = 'course-v1:MITxT+FIN.CFx';    

Additional Context

[github-actions]

🔎 ol-dbt impact — column-level blast radius

0 breaking, 0 warning, 1 info across 1 changed model(s).

Details

• ℹ️ enrollment_detail_report — enrollment_key → 0 downstream model(s)

_{Posted by ol-dbt impact (annotate-only — does not block merge).}

[Copilot]

Pull request overview

This PR updates the enrollment_detail_report dbt model to eliminate two confirmed join fan-out sources that could produce duplicate rows and inconsistent attribute values after the shift to dimensional models. It also adds a stable surrogate identifier (enrollment_key) to make row-level uniqueness easier to audit downstream.

Changes:

• Filter dim_course to is_current = true to prevent SCD2 multi-version joins from producing duplicate enrollments / outdated course titles.
• Deduplicate and join coupon/discount names by both discount_code and platform to prevent cross-platform coupon name mismatches.
• Expose enrollment_key in the report output and add not_null + unique (warn-severity) tests in the reporting schema YAML.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/ol_dbt/models/reporting/enrollment_detail_report.sql	Prevents course-title and coupon-name fan-out by constraining joins to current course rows and platform-scoped discount names; adds enrollment_key to output.
src/ol_dbt/models/reporting/_reporting__models.yml	Documents the new enrollment_key column and adds not_null + warn-severity unique tests for tracking/reporting duplicate-row issues.

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[KatelynGit]

LGTM