Release 0.138.3

[odlbot]

cp-at-mit

• restrict enrolling into b2b courses from the enrollment api (restrict enrolling into b2b courses from the enrollment api #3306) (000601db)
• 10129 attach endpoint doesnt error when the contract is full (10129 attach endpoint doesnt error when the contract is full #3293) (a6c7b1aa)

[github-actions]

OpenAPI Changes

Show/hide ## Changes for v0.yaml:

## Changes for v0.yaml:


## Changes for v1.yaml:


## Changes for v2.yaml:

Unexpected changes? Ensure your branch is up-to-date with main (consider rebasing).

[sentry]

Bug: The create() method returns None on enrollment failure, causing an AttributeError and a 500 error in the view layer when serializing the response.
_{Severity: HIGH}

Suggested Fix

Instead of returning None when successful_enrollments is empty, the create() method should raise a serializers.ValidationError with an appropriate error message. This will allow the view to handle the failure gracefully and return a 400 Bad Request response.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: courses/serializers/v1/courses.py#L190

Potential issue: The `CourseRunEnrollmentSerializer.create()` method returns `None` if
the `successful_enrollments` list is empty, which can happen if an enrollment fails in
the `create_run_enrollments()` function. The `UserEnrollmentsApiViewSet` uses Django
REST Framework's `CreateModelMixin`, which expects a model instance from `create()`.
When it receives `None`, it attempts to serialize it, leading to an `AttributeError`
when accessing attributes on the `None` object. This causes the API to return a 500
error instead of a meaningful error message indicating the enrollment failure.

_{Did we get this right? 👍 / 👎 to inform future reviews.}