Drop EventDate from RestraintEvent key

Summary of outcomes for Data Standard 2.1

• Problem Addressed: The current key for RestraintEvent contains the date field EventDate.
• High-level Reasoning: Including dates in keys is not a best practice, as dates tend to be volatile and subject to mis-entry into systems. Additionally, the remaining parts of the key (SchoolId and RestraintEventIdentifier) should be sufficient to guarantee uniqueness.
• Changes Made: Changed EventDate from part of the identity of RestraintEvent domain entity to make it required instead

Original ticket description follows:

The current RestraintEvent entity includes an EventDate as part of the key. The proposal is to drop that field from the key for two reasons:

• Dates are by their very nature volatile, and subject to mis-entry into systems
• The current key contains a SchoolID and a RestraintEventIdentifier which should be sufficient to guarantee uniqueness within a LEA or SEA use context.