Add tests for Guest model and corresponding fixtures

Introduce unit tests for the Guest model covering properties, methods, and behaviors such as creation, status updates, and permissions. Add `guest_fixture` in `conftest.py` to streamline reusable test setup for Guest instances.

backend/tests/conftest.py

@@ -4,7 +4,7 @@ import uuid
 from app.models.user import User
 from app.utils.test_utils import setup_test_db, teardown_test_db
 from app.models import GiftItem, GiftStatus, GiftPriority, RSVP, RSVPStatus, EventMedia, MediaType, MediaPurpose, \
-    EventTheme
+    EventTheme, Guest, GuestStatus
 
 
 @pytest.fixture(scope="function")
@@ -138,3 +138,35 @@ def event_theme_fixture(db_session):
     db_session.add(event_theme)
     db_session.commit()
     return event_theme
+
+import uuid
+from datetime import datetime, timezone
+from app.models.guest import Guest, GuestStatus
+
+
+@pytest.fixture
+def guest_fixture(db_session, mock_user):
+    """
+    Fixture to create and return a default Guest instance.
+    """
+    guest = Guest(
+        id=uuid.uuid4(),
+        event_id=uuid.uuid4(),
+        invited_by=mock_user.id,
+        full_name="John Doe",
+        email="johndoe@example.com",
+        phone="1234567890",
+        invitation_code="INV123456",
+        status=GuestStatus.INVITED,
+        max_additional_guests=2,
+        actual_additional_guests=1,
+        invitation_sent_at=datetime.now(timezone.utc),
+        dietary_restrictions="None",
+        notes="VIP Guest",
+        custom_fields={"allergies": "None", "special_request": "Near the stage"},
+        is_blocked=False,
+        can_bring_guests=True,
+    )
+    db_session.add(guest)
+    db_session.commit()
+    return guest