.z.pw:f
Where f is a binary function, .z.pw is evaluated after the -u/-U
checks, and before .z.po when opening a new connection to a kdb+ session.
The arguments are the user ID (as a symbol) and password (as a string) to be verified; the result is a boolean atom.
As .z.pw is simply a function it can be used to implement rules such as “ordinary users can sign on only
between 0800 and 1800 on weekdays” or can go out to external resources like an LDAP directory.
If .z.pw returns 0b the task attempting to establish the connection will get an 'access
error.
The default definition is {[user;pswd]1b}