feat: implement method to return a user's transit agency

benefits/core/models.py

@@ -8,7 +8,7 @@
 
 from django.conf import settings
 from django.core.exceptions import ValidationError
-from django.contrib.auth.models import Group
+from django.contrib.auth.models import Group, User
 from django.db import models
 from django.urls import reverse
 
@@ -435,3 +435,13 @@ def all_active():
         """Get all TransitAgency instances marked active."""
         logger.debug(f"Get all active {TransitAgency.__name__}")
         return TransitAgency.objects.filter(active=True)
+
+    @staticmethod
+    def for_user(user: User):
+        group = user.groups.first()
+
+        if group is not None:
+            # TransitAgency to Group is one-to-one, so there will be either 0 or 1 returned
+            return TransitAgency.objects.filter(group=group).first()
+        else:
+            return None

tests/pytest/core/test_models.py

@@ -1,4 +1,5 @@
 from django.conf import settings
+from django.contrib.auth.models import Group, User
 from django.core.exceptions import ValidationError
 
 import pytest
@@ -464,3 +465,18 @@ def test_TransitAgency_all_active(model_TransitAgency):
     assert len(result) > 0
     assert model_TransitAgency in result
     assert inactive_agency not in result
+
+
+@pytest.mark.django_db
+def test_TransitAgency_for_user(model_TransitAgency):
+    group = Group.objects.create(name="test_group")
+
+    agency_for_user = TransitAgency.by_id(model_TransitAgency.id)
+    agency_for_user.pk = None
+    agency_for_user.group = group
+    agency_for_user.save()
+
+    user = User.objects.create_user(username="test_user", email="[email protected]", password="test", is_staff=True)
+    user.groups.add(group)
+
+    assert TransitAgency.for_user(user) == agency_for_user