The strategy of hex encoding a random byte array only uses the
following characters:
0123456789abcdef
Instead of the entire bootstrapping token character set:
0123456789abcdefghijklmnopqrstuvwxyz
Update the token generation to use the entire character set. This
increases the token secret from 48 bits of entropy to ~82 bits.
256^8 (1.8e+19) vs. 36^16 (7.9e+24).
8debdc1501