feat(mfa): add recovery code crypto primitives

[fadymak]

This PR adds the pieces necessary to generate the recovery codes.

• The codes are lowercase, base32 in their canonical form
  • We normalize inputs to allow users to enter codes like "ABCD-EFGH" and compare them consistently as "abcdefgh"
• Codes are hashed and salted using argon2id
  • They're stored as PHC strings to be able to change parameters in the future without breaking existing hashes
  • argon2id was chosen because:
    • We allow configurable lengths of codes and should securely store the hashes in the worst case (e.g.: 10 character codes)
    • It doesn't have the 72-byte limit from bcrypt (more of a safe guard than a realistic code length)
    • NIST recommends using a password hashing scheme + salting for recovery codes < 112 bits

Note

This argon2 hash parsing and comparison is intentionally separate from the password one as they serve different purposes and will likely evolve independently so I didn't want to couple them.