BellSchedule.GradeLevel should likely be an optional collection and not part of key

Summary of outcomes for Data Standard 2.1

• Problem Addressed: Cardinality of BellSchedule.GradeLevel requires a separate record for each grade level, even if bell schedules are otherwise identical.
• High-level Reasoning: A BellSchedule may apply to multiple grade levels in a school, but the current cardinality only allows one grade level per bell schedule record. GradeLevel is currently part of the key, but the remaining parts of the key (School and BellScheduleName) are sufficient to establish uniqueness.
• Changes Made: Changed BellSchedule.GradeLevel from part of the identity to optional collection

Original ticket description follows:

It seems like BellSchedule.GradeLevel should likely be an optional collection for a few reasons:

• This information seems informational
• It seems like a BellSchedule could apply to multiple grade levels (probably a whole school in many cases)