refactor: Extract core functionality of enrollment api in a python api to avoid REST calls from edx-enterprise (#28202)

* feat: Refactor out non REST portions of enrollment api from enrollment POST method

For use with edx-enterprise to avoid making REST calls for bulk enrollment and other use cases

ENT-4746

* feat: Remove unused test

Testing is covered by test_views

* refactor: isort

isort fixes

* docs: ADR for why this change

ADR

ENT-4746

* test: Fix test failure by restoring course_id to correct object

* test: Test fix

* refactor: pylint fixes

* refactor: raise from to avoid pylint error

* refactor: Start to work toward a util in enterprise_support instead of refactoring this endpoint

* feat: Add util function in enterprise_support to eventually handle enrollment, only used by bulk enrollment for now

* feat: One more revised idea, this time low risk in edx platform and also helps address enterprise specific flow. testing pending

* feat: syntax and unused constant

* feat: Restore view and add new util function to use in edx-enterprise instead

* feat: breakpoint

* unused import

* feat: don't fail on existing enrollment

* docs: ADR update

* docs: docstring minor update

* test: unit test add_user_to_course_cohort

* refactor: imports

* feat: remove unused error classes

* refactor: lint

* test: Test cases

* test: Two more tests for negative cases

* feat: missing init.py file

* test: Fix tests to use correct user mock

* unused import

* refactor: Review feedback, test fixes, needs rebase now

* feat: rebase changes

* feat: keep audit_log with similar logic as in the view

* refactor: Review feedback, test constant usage

openedx/core/djangoapps/enrollments/errors.py

@@ -7,6 +7,7 @@ class CourseEnrollmentError(Exception):
     Describes any error that may occur when reading or updating enrollment information for a user or a course.
 
     """
+
     def __init__(self, msg, data=None):
         super().__init__(msg)
         # Corresponding information to help resolve the error.

openedx/core/djangoapps/enrollments/tests/test_utils.py

@@ -0,0 +1,30 @@
+"""
+Tests for enrollment utils
+"""
+import unittest
+from unittest.mock import patch
+
+from openedx.core.djangoapps.enrollments.utils import add_user_to_course_cohort
+
+
+class EnrollmentUtilsTest(unittest.TestCase):
+    """
+    Enrollment utils test cases
+    """
+    @patch("openedx.core.djangoapps.enrollments.utils.add_user_to_cohort")
+    @patch("openedx.core.djangoapps.enrollments.utils.get_cohort_by_name")
+    def test_adds_user_to_cohort(self, mock_get_cohort_by_name, mock_add_user_to_cohort):
+        user = {}
+        mock_get_cohort_by_name.return_value = "a_cohort"
+
+        add_user_to_course_cohort("a_cohort", "a_course_id", user)
+        assert mock_add_user_to_cohort.call_count == 1
+
+    @patch("openedx.core.djangoapps.enrollments.utils.add_user_to_cohort")
+    @patch("openedx.core.djangoapps.enrollments.utils.get_cohort_by_name")
+    def test_does_not_add_user_to_cohort(self, mock_get_cohort_by_name, mock_add_user_to_cohort):
+        user = {}
+        mock_get_cohort_by_name.return_value = "a_cohort"
+
+        add_user_to_course_cohort(None, "a_course_id", user)
+        assert mock_add_user_to_cohort.call_count == 0

openedx/core/djangoapps/enrollments/utils.py

@@ -0,0 +1,20 @@
+"""
+Utils for use in enrollment code
+"""
+import logging
+from openedx.core.djangoapps.course_groups.cohorts import add_user_to_cohort, get_cohort_by_name
+
+logger = logging.getLogger(__name__)
+
+
+def add_user_to_course_cohort(cohort_name, course_id, user):
+    """
+    If cohort_name is provided, adds user to the cohort
+    """
+    if cohort_name is not None:
+        cohort = get_cohort_by_name(course_id, cohort_name)
+        try:
+            add_user_to_cohort(cohort, user)
+        except ValueError:
+            # user already in cohort, probably because they were un-enrolled and re-enrolled
+            logger.exception('Cohort re-addition')