[dataimport] introduce usage of MetadataGenerator into the massive store
This allows more flexibility and code sharing w/ nohook store.
Closes #10338621
.._ajax:Ajax----CubicWeb provides a few helpers to facilitate *javascript <-> python* communications.You can, for instance, register some python functions that will becomecallable from javascript through ajax calls. All the ajax URLs are handledby the :class:`cubicweb.web.views.ajaxcontroller.AjaxController` controller...automodule:: cubicweb.web.views.ajaxcontroller