Migration Hash = sha512(perUserSalt + md5(user supplied password))
2. If authentication via migration hash is successful:
- Use the user's provided password and calculate the New Hash per the algorithm defined above.
- Overwrite the Migration Hash with the New Hash
3. If authentication via migration hash is NOT successful:
- The user may already be on the New Hash. Attempt to directly authenticate using the new hash. If this fails, then the password provided by the user is wrong.