ConvertToKey generates a private key using the recovery code as a seed.

Generate creates a new random recovery code using a cryptographically secure random number generator.

Validate returns an error if the recovery code is not valid or nil otherwise.

Version returns the version that this recovery code corresponds to.

Alphabet contains all upper-case characters except for numbers/letters that look alike.

AlphabetLegacy constains the letters that pre version 2 recovery codes can contain.

CurrentVersion defines the current version number for the recovery codes.