[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
if versions_map['cubicweb'][0] == (3, 7, 4):
config['http-session-time'] *= 60
config['cleanup-session-time'] *= 60
config['cleanup-anonymous-session-time'] *= 60