cubicweb #2481820 session.security_enabled has erroneous default values for its arguments [done]

should be None, not False, else security will be unintendly disabled (eg with session.security_enabled() disable read and write security, which is very counter intuitive and force to specify both values when you want to disable only one (eg session.security_enabled(read=False, write=True) to disable read security, while session.security_enabled(read=False) should be enough.

done in3.16.0
load left0.000
closed by#0d2fb4604265 [session] fix arguments default value and promote usage of security_enabled as session method. Closes #2481820