Get gender from id

[tgranqvist]

Add a function to get gender from the personal ID code.

CREATE OR REPLACE FUNCTION get_gender_from_hetu(hetu CHAR(11))
RETURNS gender AS $$
DECLARE
  id_part INT;
  gender gender := 'male'::gender;
BEGIN
  id_part := SUBSTRING(hetu, 8, 3)::INT;
  
  IF id_part % 2 = 0 THEN
    gender := 'female'::gender;
  END IF;
  
  RETURN gender;
END;
$$ LANGUAGE plpgsql IMMUTABLE;