🔧(backend) add posthog configuration

We add the posthog configuration to the project.
We will expose the posthog configuration to the
frontend.

src/backend/core/api/viewsets.py

@@ -1124,6 +1124,7 @@ class ConfigView(drf.views.APIView):
             "ENVIRONMENT",
             "FRONTEND_THEME",
             "MEDIA_BASE_URL",
+            "POSTHOG_KEY",
             "LANGUAGES",
             "LANGUAGE_CODE",
             "SENTRY_DSN",

src/backend/core/tests/test_api_config.py

@@ -20,6 +20,7 @@ pytestmark = pytest.mark.django_db
     CRISP_WEBSITE_ID="123",
     FRONTEND_THEME="test-theme",
     MEDIA_BASE_URL="http://testserver/",
+    POSTHOG_KEY={"id": "132456", "host": "https://eu.i.posthog-test.com"},
     SENTRY_DSN="https://sentry.test/123",
 )
 @pytest.mark.parametrize("is_authenticated", [False, True])
@@ -41,5 +42,6 @@ def test_api_config(is_authenticated):
         "LANGUAGES": [["en-us", "English"], ["fr-fr", "French"], ["de-de", "German"]],
         "LANGUAGE_CODE": "en-us",
         "MEDIA_BASE_URL": "http://testserver/",
+        "POSTHOG_KEY": {"id": "132456", "host": "https://eu.i.posthog-test.com"},
         "SENTRY_DSN": "https://sentry.test/123",
     }

src/backend/impress/settings.py

@@ -390,6 +390,11 @@ class Base(Configuration):
         None, environ_name="FRONTEND_THEME", environ_prefix=None
     )
 
+    # Posthog
+    POSTHOG_KEY = values.DictValue(
+        None, environ_name="POSTHOG_KEY", environ_prefix=None
+    )
+
     # Crisp
     CRISP_WEBSITE_ID = values.Value(
         None, environ_name="CRISP_WEBSITE_ID", environ_prefix=None