[session] deprecate `hijack_user` method
The semantic of this method is wicked and lead to very hard violation of sanity.
(multiple transaction using the very same cursors). We deprecated the API to be
able to drop it as soon as possible.
The method was added long ago for some notification trick. It is not needed
since we sent notification on ``postcommit_event``.
(closes #2781782)
[system]
db-driver = postgres
db-host = localhost
db-port = 5433
adapter = native
db-name = cw_fti_test
db-encoding = UTF-8
db-user = syt
db-password = syt
[admin]
login = admin
password = gingkow