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.

[hooks/security] Defer entity permission checks to an Operation. Some of these checks may currently happen twice within the same transaction and be costly. This should be semantically safe. If people rely on some internal transaction ordering to be allowed early (thus pass) while the condition wouldn't be met at precommit time, their application is broken. It however seems unlikely to happen in the real life (tm). Closes #2932033

[schema] drop very old bw compat (pre 3.5.10) Closes #2925085.