remove 3.8 bw compat - cwconfig: old keys such as depends_cubes and non-dict dependencies - cwctl: fall back to docstring if no short descr, forget 'short_descr' - dbapi: session_data, get_session_data, set_session_data, del_session_data - dbapi & testlib, session: eid_key is gone - migractions: cachekey is gone - doc/datamodel/definition, schemaserial: BoundConstraint -> BoundaryConstraint - formwidgets: separator - primary view: render_entity_metadata Related to #2782004.

usr/lib/PY_VERSION/*-packages/cubicweb/web
usr/share/cubicweb/cubes/shared/data
usr/share/cubicweb/cubes/shared/wdoc