get the most recent BMI data. the handler function will be called with a `bmi` object containing `*value: number*`, `*startDate: ISO8601Timestamp*`, and `*endDate: ISO8601Timestamp*`. The BMI value may be very old so the sample dates are provided as well. *should apply this to all other RCT types*
get the most recent BMI data. the handler function will be called with a `bmi` object containing *`value: number`*, *`startDate: ISO8601Timestamp`*, and *`endDate: ISO8601Timestamp`*. The BMI value may be very old so the sample dates are provided as well. *should apply this to all other RCT types*