Remove AssessmentFamily from the model and APIs

Summary of outcomes for Data Standard 2.1

• Problem Addressed: There does not appear to be sufficient value in the AssessmentFamily domain entity to warrant the additional model complexity.
• High-level Reasoning: Though several implementations are grouping Assessments into AssessmentFamilies, the additional metadata in the AssessmentFamily domain entity is not thought to be highly utilized. AssessmentFamily could therefore be accommodated as an optional property on Assessment rather than as a domain entity, reducing some of the model complexity and opportunity for variability in implementation.
• Changes Made: Removed the AssessmentFamily domain entity from the model and replaced the reference to AssessmentFamily in the Assessment domain entity with optional string AssessmentFamily of max length 60; Made Assessment.Namespace required (since it was required in AssessmentFamily)

Original ticket description follows:

There is little evidence that AssessmentFamily has been useful in field implementations and it add complexity to the model and to APIs, including raising questions about what "standard" usage of the entity looks like . As a result, there is an imbalance between its utility and its costs. The proposed direction is to remove it from the model.

From the perspective of a user of Ed-Fi APIs, the Assessment / AssessmentFamily association creates ambiguity in how to use data coming from these entities. It does this mainly due to way the two entities repeat several fields: Subject, GradeLevel, Title, etc.

When field values differ between Assessment and AssessmentFamily, which entity's data is seen as authoritative. Assessment? AssessmentFamily? Both (i.e. they are different), or neither (i.e. there's a problem)?

Different systems may have different answers to such questions, which introduces different semantics and will hurt interoperability. Alternatively, the data standard could supply semantics and answers to that usage, but at this point that seems overkill because the value of the abstraction is unclear in the field. The suggested path is to remove the entity from the model.