🚩(frontend) feature flag on blocking edition

If users were not connected to the collaboration
server, they were not be able to edit documents.

We decided to add a feature flag on this feature
as it can be quite restrictive.
We can now enable or disable this feature at runtime
thanks to the env variable
"COLLABORATION_WS_NOT_CONNECTED_READY_ONLY".

src/backend/impress/settings.py

@@ -413,6 +413,11 @@ class Base(Configuration):
     COLLABORATION_WS_URL = values.Value(
         None, environ_name="COLLABORATION_WS_URL", environ_prefix=None
     )
+    COLLABORATION_WS_NOT_CONNECTED_READY_ONLY = values.BooleanValue(
+        False,
+        environ_name="COLLABORATION_WS_NOT_CONNECTED_READY_ONLY",
+        environ_prefix=None,
+    )
 
     # Frontend
     FRONTEND_THEME = values.Value(