[Building Sakai] proposal to deal with Gradebook / Lessons interaction

[Charles Hedrick]

I propose adding to ExternalAssignmentProvider one more method:

registerInterceptor (class)

the class has the same profile as the existing ones, but with Boolean rather than boolean.  The methods are prepared to handle assessment IDs from any tool, not just their own. They will return a value, or null if they're not interested. 

If more than one tool register interceptors they should all be called. The first one to return a value is used. If they return null, go on to the next one.

The Lesons implementation will guarantee to use sufficient caching that they do not add significant overhead for items they're not interested in.

My understanding is that some tool other than Lessons does something similar with groups. Hence a general design rather than Lesson-specific hacks.