User Configurable Flow at /idp/

[Tom Zeller]

> ... not possible in v3 since the servlet-mapping for the idp
> servlet is /*.

I was never really sure about that servlet-mapping.

> Aside from the slight complication of getting a sane flow ID for the
> /idp/ URI, it seems like this should be straightforward: ship a flow
> under /flows that renders a 404 by default, but that the user can
> modify to achieve other behaviors. As for getting a flow ID for what
> is effectively an empty path, you could extend DefaultFlowUrlHandler
> to have some special handling for the root context path.
>
> I'm happy to work up a patch for this functionality, but I wanted to
> float it here to get feedback.

A user-configurable default flow sounds great.

Not real excited about extending DefaultFlowUrlHandler, just because
it's one more extension point, but I don't know what the alternatives
are, at the moment.