feat: add an assignments SAP model

enterprise_access/apps/subsidy_access_policy/admin.py

@@ -127,3 +127,44 @@ def per_learner_spend_limit_dollars(self, obj):
         if obj.per_learner_spend_limit is None:
             return None
         return cents_to_usd_string(obj.per_learner_spend_limit)
+
+
+@admin.register(models.AssignedLearnerCreditAccessPolicy)
+class LearnerContentAssignmentAccessPolicy(DjangoQLSearchMixin, BaseSubsidyAccessPolicyMixin):
+    """
+    Admin configuration for AssignedLearnerCreditAccessPolicy.
+    """
+    search_fields = (
+        'uuid',
+        'display_name',
+        'enterprise_customer_uuid',
+        'catalog_uuid',
+        'subsidy_uuid',
+    )
+
+    fieldsets = [
+        (
+            'Base configuration',
+            {
+                'fields': [
+                    'enterprise_customer_uuid',
+                    'display_name',
+                    'description',
+                    'active',
+                    'catalog_uuid',
+                    'subsidy_uuid',
+                    'created',
+                    'modified',
+                ]
+            }
+        ),
+        (
+            'Spend limits',
+            {
+                'fields': [
+                    'spend_limit',
+                    'policy_spend_limit_dollars',
+                ]
+            }
+        ),
+    ]

enterprise_access/apps/subsidy_access_policy/migrations/0015_assigned_learner_credit_policy.py

@@ -0,0 +1,39 @@
+# Generated by Django 3.2.20 on 2023-08-28 13:25
+
+from django.db import migrations
+import enterprise_access.apps.subsidy_access_policy.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('subsidy_access_policy', '0014_add_policy_display_name'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='AssignedLearnerCreditAccessPolicy',
+            fields=[
+            ],
+            options={
+                'proxy': True,
+                'indexes': [],
+                'constraints': [],
+            },
+            bases=(enterprise_access.apps.subsidy_access_policy.models.CreditPolicyMixin, 'subsidy_access_policy.subsidyaccesspolicy'),
+        ),
+        migrations.CreateModel(
+            name='HistoricalAssignedLearnerCreditAccessPolicy',
+            fields=[
+            ],
+            options={
+                'verbose_name': 'historical assigned learner credit access policy',
+                'ordering': ('-history_date', '-history_id'),
+                'get_latest_by': 'history_date',
+                'proxy': True,
+                'indexes': [],
+                'constraints': [],
+            },
+            bases=('subsidy_access_policy.historicalsubsidyaccesspolicy',),
+        ),
+    ]

enterprise_access/apps/subsidy_access_policy/models.py

@@ -9,6 +9,7 @@
 import requests
 from django.conf import settings
 from django.core.cache import cache as django_cache
+from django.core.exceptions import ValidationError
 from django.db import models
 from django_extensions.db.models import TimeStampedModel
 from edx_django_utils.cache.utils import get_cache_key
@@ -770,3 +771,41 @@ def remaining_balance_per_user(self, lms_user_id=None):
         """
         spent_amount = self.transactions_for_learner(lms_user_id)['aggregates'].get('total_quantity') or 0
         return self.per_learner_spend_limit - spent_amount
+
+
+class AssignedLearnerCreditAccessPolicy(CreditPolicyMixin, SubsidyAccessPolicy):
+    """
+    Policy based on LearnerContentAssignments, backed by a learner credit type of subsidy.
+
+    .. no_pii: This model has no PII
+    """
+    objects = PolicyManager()
+
+    class Meta:
+        """ Meta class for this policy type. """
+        proxy = True
+
+    def clean(self):
+        """
+        Policies of this type must have a defined spend_limit,
+        and they can *not* define either of the per-learner limits.
+        """
+        if self.spend_limit is None:
+            raise ValidationError(f'{self} must define a spend_limit.')
+        if self.per_learner_spend_limit is not None:
+            raise ValidationError(f'{self} must not define a per-learner spend limit.')
+        if self.per_learner_enrollment_limit is not None:
+            raise ValidationError(f'{self} must not define a per-learner enrollment limit.')
+
+    def save(self, *args, **kwargs):
+        """
+        This type of policy must always have an access_method of "assigned".
+        """
+        self.access_method = AccessMethods.ASSIGNED
+        super().save(*args, **kwargs)
+
+    def can_redeem(self, lms_user_id, content_key, skip_customer_user_check=False):
+        raise NotImplementedError
+
+    def redeem(self, lms_user_id, content_key, all_transactions, metadata=None):
+        raise NotImplementedError