feat: add AirShelf core implementation

core/backend/apps/accounts/tests.py

@@ -0,0 +1,29 @@
+from django.test import TestCase
+from rest_framework.test import APIClient
+
+from apps.accounts.models import Team, TeamMember, User
+from apps.billing.models import CreditAccount
+
+
+class AuthApiTests(TestCase):
+    def test_register_creates_user_team_member_credit_account_and_token(self):
+        client = APIClient()
+        response = client.post(
+            "/api/auth/register/",
+            {
+                "username": "new-owner",
+                "password": "strong-password",
+                "email": "owner@example.com",
+                "team_name": "Launch Team",
+            },
+            format="json",
+        )
+
+        self.assertEqual(response.status_code, 201)
+        self.assertIn("token", response.data)
+        user = User.objects.get(username="new-owner")
+        team = Team.objects.get(name="Launch Team")
+        self.assertEqual(team.owner, user)
+        self.assertTrue(TeamMember.objects.filter(team=team, user=user, role=TeamMember.Role.OWNER).exists())
+        self.assertTrue(CreditAccount.objects.filter(team=team).exists())
+