✨(backend) introduce a creation callback endpoint

Necessary in cross browser context situation, where we need to
pass data of a room newly created between two different windows.

This happens in Calendar integration.

src/backend/core/tests/rooms/test_api_rooms_create.py

@@ -2,6 +2,9 @@
 Test rooms API endpoints in the Meet core app: create.
 """
 
+# pylint: disable=W0621,W0613
+from django.core.cache import cache
+
 import pytest
 from rest_framework.test import APIClient
 
@@ -11,6 +14,15 @@ from ...models import Room
 pytestmark = pytest.mark.django_db
 
 
+@pytest.fixture
+def reset_cache():
+    """Provide cache cleanup after each test to maintain test isolation."""
+    yield
+    keys = cache.keys("room-creation-callback_*")
+    if keys:
+        cache.delete(*keys)
+
+
 def test_api_rooms_create_anonymous():
     """Anonymous users should not be allowed to create rooms."""
     client = APIClient()
@@ -26,7 +38,7 @@ def test_api_rooms_create_anonymous():
     assert Room.objects.exists() is False
 
 
-def test_api_rooms_create_authenticated():
+def test_api_rooms_create_authenticated(reset_cache):
     """
     Authenticated users should be able to create rooms and should automatically be declared
     as owner of the newly created room.
@@ -49,6 +61,33 @@ def test_api_rooms_create_authenticated():
     assert room.slug == "my-room"
     assert room.accesses.filter(role="owner", user=user).exists() is True
 
+    rooms_data = cache.keys("room-creation-callback_*")
+    assert not rooms_data
+
+
+def test_api_rooms_create_generation_cache(reset_cache):
+    """
+    Authenticated users creating a room with a callback ID should have room data stored in cache.
+    """
+    user = UserFactory()
+
+    client = APIClient()
+    client.force_login(user)
+
+    response = client.post(
+        "/api/v1.0/rooms/",
+        {"name": "my room", "callback_id": "1234"},
+    )
+
+    assert response.status_code == 201
+    room = Room.objects.get()
+    assert room.name == "my room"
+    assert room.slug == "my-room"
+    assert room.accesses.filter(role="owner", user=user).exists() is True
+
+    room_data = cache.get("room-creation-callback_1234")
+    assert room_data.get("slug") == "my-room"
+
 
 def test_api_rooms_create_authenticated_existing_slug():
     """

src/backend/core/tests/rooms/test_api_rooms_creation_callback.py

@@ -0,0 +1,98 @@
+"""
+Test rooms API endpoints in the Meet core app: creation callback functionality.
+"""
+
+# pylint: disable=W0621,W0613
+from django.core.cache import cache
+
+import pytest
+from rest_framework.test import APIClient
+
+from ...factories import UserFactory
+
+pytestmark = pytest.mark.django_db
+
+
+# Tests for creation_callback endpoint
+
+
+@pytest.fixture
+def reset_cache():
+    """Provide cache cleanup after each test to maintain test isolation."""
+    yield
+    keys = cache.keys("room-creation-callback_*")
+    if keys:
+        cache.delete(*keys)
+
+
+def test_api_rooms_create_anonymous(reset_cache):
+    """Anonymous user can retrieve room data once using a valid callback ID."""
+    client = APIClient()
+    cache.set("room-creation-callback_123", {"slug": "my room"})
+    response = client.post(
+        "/api/v1.0/rooms/creation-callback/",
+        {
+            "callback_id": "123",
+        },
+    )
+
+    assert response.status_code == 200
+    assert response.json() == {"status": "success", "room": {"slug": "my room"}}
+
+    # Data should be cleared after retrieval
+    response = client.post(
+        "/api/v1.0/rooms/creation-callback/",
+        {
+            "callback_id": "123",
+        },
+    )
+
+    assert response.status_code == 200
+    assert response.json() == {"status": "success", "room": {}}
+
+
+def test_api_rooms_create_empty_cache():
+    """Valid callback ID return empty room data when nothing is stored in the cache."""
+    client = APIClient()
+
+    response = client.post(
+        "/api/v1.0/rooms/creation-callback/",
+        {
+            "callback_id": "123",
+        },
+    )
+
+    assert response.status_code == 200
+    assert response.json() == {"status": "success", "room": {}}
+
+
+def test_api_rooms_create_missing_callback_id():
+    """Requests without a callback ID properly fail with a 400 status code."""
+    client = APIClient()
+
+    response = client.post(
+        "/api/v1.0/rooms/creation-callback/",
+        {},
+    )
+
+    assert response.status_code == 400
+
+
+def test_api_rooms_create_authenticated(reset_cache):
+    """Authenticated users can also successfully retrieve room data using a valid callback ID"""
+    user = UserFactory()
+
+    client = APIClient()
+    client.force_login(user)
+
+    cache.set("room-creation-callback_123", {"slug": "my room"})
+
+    response = client.post(
+        "/api/v1.0/rooms/creation-callback/",
+        {
+            "callback_id": "123",
+        },
+    )
+
+    assert response.status_code == 200
+    assert response.json() == {"status": "success", "room": {"slug": "my room"}}