A CWA with anonymous browsing can answer an OPDS request whatever the
password, so each password logged a user in to Bindery. Bindery now
tests CWA with a login that cannot exist, and refuses OPDS logins if
CWA accepts it. A login check no longer shares the session of the
account of Bindery. The CWA account stays optional for a CWA that asks
for no login, and a missing account now gets its own message.