Prevent jumping into a flow without going through the front door.

RS> One observation is with regards to access to flow scoped data. When
RS> using the provided buttons, everything works as it should, i.e. flow
RS> scoped data is created at the point of entering the flow and
RS> destroyed when the flow is exited. However, it is easy to bypass the
RS> entry and exit points. For example I can go directly to a page
RS> associated with a flow without entering the flow, and if the page
RS> tries to access flow data, the result would be
RS> ContextNotActiveException.

One could argue that such an exception is the right response. The
context is indeed not active. However, if you are not using any flow
scoped data, such an exception would not be thrown, and it would give
the impression that the navigation is supported.

I think we can add some language to the spec to detect these "jump in"
cases.
#### Affected Versions
[2.2]

Start by reviewing the Jakarta Faces specification sections covering flow entry and exit points and flow-scoped data. Define the proposed language for direct navigation into a flow, and confirm that it consistently addresses cases where flow-scoped data is not accessed.

Written by the indexing model from the issue text.