@nexedi I still have to write the documentation to explain in a bit more details how to prepare migration of a Product to ZODB Components and a few general notes (that's why the commit Document Dynamic classes is still WIP) but I think the commits messages already explain enough so I have created this merge request to have some feedbacks.
The main commit (Allow migration of {Interface,Mixin,Module,Tool} from Business Template UI and on all Products (not only Products.ERP5).) is WIP because I have a few things to clean up here and there and also to write a few Unit Tests, but all the features have been implemented I think.
I have done ERP5ShortMessage migration following a suggestion from Jérome because it is not so big, uses all ZODB Components types (except Mixin) and does not need to be split into several bt5s. Once this has been merged, the next step is to migrate other Products one by one.