canonicalize
Returns a token semantically equal to token but using only characters from the Crockford Base32 alphabet. This maps visually similar characters like o to the corresponding encoding character like 0. Spaces are omitted.
Call this when accepting tokens that may have been transcribed by a user. It is not necessary to canonicalize tokens that haven't been manually entered; they will already be in canonical form.
Throws
if token contains a character that cannot be mapped and that is not a space.