🐛(webhooks) fix special case for tchap integration

we want to use Tchap integration server for our own preprod
but it doesn't follow the same url naming convention as the
other Tchap instances, so it requires a special treatment.
This quick fix should do it.

src/backend/core/tests/utils/test_webhooks_matrix_client.py

@@ -230,6 +230,9 @@ def test_matrix_webhook__override_secret_for_tchap():
     headers = responses.calls[0].request.headers
     assert "TCHAP_TOKEN" in headers["Authorization"]
 
+    # Check correctly inferred base url from room_id
+    assert "matrix.home_server" in responses.calls[0].request.url
+
 
 ## KICK
 @responses.activate

src/backend/core/utils/matrix.py

@@ -45,7 +45,7 @@ class MatrixAPIClient:
         """Returns room id from webhook url."""
         room_id = webhook_url.split("/room/")[1]
         base_url = room_id.split(":")[1]
-        if "tchap.gouv.fr" in webhook_url:
+        if "tchap.gouv.fr" in webhook_url and "i.tchap.gouv.fr" not in webhook_url:
             base_url = f"matrix.{base_url}"
         return f"https://{base_url}/_matrix/client/v3/rooms/{room_id}"