Conditional subflows

[Cantor, Scott]

I just checked in a placeholder of sorts for a feature I think we need a
standard way to express, which is conditionally executed subflows in the
middle of our logic, to let people customize the UI for various events.

(The specific use case for this was being able to inject a subflow to
respond to things like expired passwords or a locked account, without
needing to change/override/edit the actual form login flow.)


I'm not sure the best way to do it, but I think there are two options, or
a third that would be the best but I don't know how to do.

What I did was create a dummy flow that just echoes "proceed" and allows
itself to be called as a subflow without actually doing anything. Then I
called it by conditionally doing a <transition> that runs conditionally
and calls the subflow.

What I would *like* to do is further conditionalize that subflow call by
having a boolean property that can be turned on or off, and set via
property file. But I don't know how to do property overrides inside
webflow config files.

What I could do is define a Boolean bean set based on a property, and then
decision on that bean in the flow definition. My feeling was that was
extra work for no real purpose other than bypassing a fast subflow call
that doesn't hurt anything.

-- Scott