Life Path Number

Is it possible to propose the calculation of the life path number via a Typeform calculator?
I have tried different variants, unfortunately without success.

Can you help me?

A person's Life Path Number is calculated by adding each individual number in that person's date of birth, until it is reduced to a single digit number.

Complete the function that accepts a date of birth (as a string) in the following format: "yyyy-mm-dd". The function shall return a one digit integer between 1 and 9 which represents the Life Path Number of the given date of birth.

Example

For example, Albert Einstein's birthday is March 14, 1879 ("1879-03-14"). The calculation of his Life Path Number would look like this:

year  :  1 + 8 + 7 + 9 = 25  -->  2 + 5 = 7
month :  0 + 3 = 3
day   :  1 + 4 = 5
result:  7 + 3 + 5 = 15  -->  1 + 5 = 6

Einstein's Life Path Number is therefore: 6

Thanks and regards,

David from naturalsandco.ch