It's easily possible for SessionManager::getSessionById() to not be
able to load the specified session and to not be able to create an empty
one by that ID, for example if the user's token changed. So change this
from an exceptional condition to an expected one, and adjust callers to
deal with it appropriately.
Let's also make the checks for invalid data structure when loading the
session from the store delete the bogus data entirely.
At the same time, let's change the silly "$noEmpty" parameter to
"$create" and make the default behavior be not to create an empty
session.
Bug: T124126
Change-Id: I085d2026d1b366b1af9fd0e8ca3d815fd8288030
SessionManager is a general-purpose session management framework, rather
than the cookie-based sessions that PHP wants to provide us.
While fallback is provided for using $_SESSION and other PHP session
management functions, they should be avoided in favor of using
SessionManager directly.
For proof-of-concept extensions, see OAuth change Ib40b221 and
CentralAuth change I27ccabdb.
Bug: T111296
Change-Id: Ic1ffea74f3ccc8f93c8a23b795ecab6f06abca72
