Expand and further clarify the way the Ed-Fi model captures gender information

Summary of outcomes for Data Standard 3.0

• Problem Addressed: Prior to v3.0, gender codes were contained in SexType, making it impossible to customize values to accommodate implementation-specific needs without modifying core. Additionally, there was some ongoing confusion as to whether the existing SexType structure was to be used to connote the biological sex assigned at birth or a person's gender identity.
• High-level Reasoning: In v3.0, all types became descriptors - allowing implementations to use custom values in the new SexDescriptor. By adding a reference to the SexDescriptor in the BirthData common type (in addition to the existing reference on Student), implementations are now able to collect the biological sex assigned at birth in addition to the official sex/gender collected for the student's record.
• Changes Made: An optional reference to the SexDescriptor was added to the BirthData common type.

Original ticket description follows:

We have been hearing reports of the limitations of the Ed-Fi data model with regards to capturing information on a person's gender. This item provides a place to aggregate field implementation evidence on the current gaps.

The attached document from Michigan provides some context. That document for example suggests that the Data Standard 2.0 definition of SexType as "A person's gender" is ambiguous in if refers to a biological identity of some kind, or a gender identity held by the individual.