Write a method, power_digit_sum, that takes a base (x) and an exponent (n) as arguments and returns the sum of the digits of x raised to the power of n. It should work for arbitrarily large n (at least up to n = 1000).
For example, power_digit_sum(2, 4) would return 7:
- 2 to the power of 4 is 16
- 1 + 6 = 7