[source/native] refactor eid generation code This set of related methods clutters the native source API. It will be better served with a dedicated eid genrator object. Related to #3526594. [jcr: allocate the eid generator in __init__]

Move entity cache from web.request.ConnectionCubicWebRequestBase to repoapi.ClientConnection ResultSet._build_entity relies on an entity cache to avoid going round in circles (stack overflow due to infinite recursion) e.g. in a postcreate script. Clear the cache at commit/rollback time to avoid unexpected side effects; and explicitly clear the cache in a few tests where we mix ORM and RQL using the same connection.

[server] Fix AttributeError in extid2eid Session._tx was renamed in cb87e831c183, use _cnx instead.

[book] Update documentation for new repoapi Quite a few things change in 3.19: - repoapi instead of dbapi - ClientConnection / Connection / Session rework - web authentication process - test APIs Closes #3638793

[utils] the json module is always available It's included since python 2.6, and we don't support earlier versions.

[fti] properly close the ProgressBar Ensures cubicweb-ctl db-rebuild-fti ends its output with a newline.

[serverctl] use repoapi for db-check, add-source, rebuild-fti commands One more step towards getting rid of dbapi.

[devtools] make get_repo_and_cnx return a repoapi ClientConnection And adjust callers accordingly (they need to use it as a context manager to open/close it properly).

[repoapi] Avoid deprecation warnings from session.id Apparently it's called session.sessionid now.

[server] some s/session/cnx/ For merely accessing the database we need a connection, not a session.