description: |-
  Patient's date of birth.
  
  Note that by convention, patients whose birthdate is unknown (rare, but can happen in certain asylum seeker cases)
  pick a date and tend to pick either `xxxx-01-01` or `xxxx-07-01`.
  Can, in rare cases, be unavailable - if birth date is not known; in that case, `null` is sent.
$ref: ./date.yaml