[IdPv3] Session Management APIs

[Chad La Joie]

I've committed the new Session APIs for IdP v3[1].  They are pretty similar in concept to the v2 APIs, but there are some structural changes I'd like to highlight.

- The session management service has been split in to two separate APIs:
   - a session store that contains methods for storing and loading sessions
   - a session resolver that provides a query-by-criteria mechanism
- A session store that persists data to cookies will be provided, this will by necessity require logic that expunges data if serialized data would be too big to write out to cookies.  This would be done in a least recently used manner.
- The provided session resolver implementation will not keep any indexes over the contained data.  This obviously means those index can't fall out of synch as was a problem a couple times in v2.
- Sessions are now created by means of a SessionFactory, so developers can extend the creation mechanism if they wish
- An authentication event can return one, and only one Principal for a user

I encourage any developer that has had to deal with sessions and session management directly to look at the new code and offer comments/questions, by replying to this email, over the next two weeks.

[1] http://svn.shibboleth.net/view/java-identity-provider/trunk/idp-authn-api/src/main/java/net/shibboleth/idp/session/

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Chad La Joie
www.itumi.biz
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