sex_at_birth vs. sex_assigned_at_birth

[wilke0818]

Currently there is logic for creating a computed field called sex_at_birth based off of gender_identity and specify_gender_identity. However, there is a "new" column in from the redcap data dictionary that already specifies sex (sex_assigned_at_birth) that is currently not being used.

I propose that the logic in b2aiprep should change to do the following:

• Use sex_assigned_at_birth as a primary data point
• If not specified, which for most it is not, continue to use gender_identity
• Fix logic of sex_at_birth which currently does not use whether individuals specified themselves as 'trans' for specify_gender_identity - there is some complexity here that I am not certain if we should do this or not