Re: Terminate the idle sessions

The following review has been posted through the commitfest application:
make installcheck-world:  tested, passed
Implements feature:       tested, passed
Spec compliant:           tested, passed
Documentation:            tested, passed

I applied this patch to the PG13 branch and generally this feature works as described. The new "idle_session_timeout"
thatcontrols the idle session disconnection is not in the default postgresql.conf and I think it should be included
therewith default value 0, which means disabled. 
 
There is currently no enforced minimum value for "idle_session_timeout" (except for value 0 for disabling the feature),
souser can put any value larger than 0 and it could be very small like 500 or even 50 millisecond, this would make any
psqlconnection to disconnect shortly after it has connected, which may not be ideal. Many systems I have worked with
have30 minutes inactivity timeout by default, and I think it would be better and safer to enforce a reasonable minimum
timeoutvalue