Remove reference to StudentAcademicRecord on CourseTranscript to increase flexibility of the model

This is a improvement proposed via conversation with Powerschool, with some field examples pulled from state projects.

The current model requires a reference to StudentAcademicRecord (SAR) on each CourseTranscript. This reflects the typical structure of a transcript report, where each period in which credits are awarded has a set of references to courses taken and grades.

However, the model is a bit awkward when there are courses that extend over semesters (or trimesters, etc. - e.g. a year-long course) where credit is awarded incrementally. Take the case of a student in a year-long and a semester course that both end at the end of the year. In this case, the system providing the data must either:

1. Break the year-long course into multiple CourseTranscripts, and attach each part to a SAR for each semester (so 1 SAR for each semester, with the year-long course "broken" into two CTs)
2. Create SARs that overlap (so 1 SAR for the year, and 1 for the semester, with the right CT attached to each

Neither model is ideal:

in #1 the CourseTranscript representation has been broken into two parts. However, arguably since credit is awarded that way, that's most accurate.
In #2, downstream systems have to reconcile multiple SARs to get an accurate picture of what is happening

If SARs were decoupled from CTs, then the SAR would just provide a summary or "header" of credit info at the end of some period (almost like an "as of" time dimension). CTs could be done in whichever way the organization felt was most accurate.

The time dimension on CT currently provided by the reference to the SAR would move to the CT. So the key of CT would be StudentID, EdOrgID, CourseCode, Term, and SchoolYear.

It is worth noting that the current model is not broken, but that this is just a suggested improvement.