[FIX] models: avoid creating XML ids for models that have not been extended

Assume module M extends model `base`.  Upon installing M, all models in the
registry are impacted by the extension, so their `_auto_init` method is
invoked.  This currently creates an XML id `M.model_X` for every model X,
including the custom models created before installing M.  Now, if we deinstall
module M, all those custom models will be removed, as they have only one XML
id, namely the one introduced by M.

Prevent the creation of XML ids for the children of an extended model to avoid
this bug.  Note that if the model extension adds a field, every instance of
that field in children models will have an XML id associated to module M.

0 files changed, 0 insertions, 0 deletions