StudentAssessment identity (key) cannot account for multiple Assessment attempts within a single day

The current key for StudentAssessment includes a Student reference, an Assessment reference and an AdministrationDate, which is a date type constrained to month, day and year only.

If the same student takes the same assessment multiple times in the same day, the model has no way to capture unique instances. This is a limitation in any context where an assessment may be taken multiple times in a single day.

The model currently seems optimized for summative assessments where such incidences would be very rare.