TODO

Fix exchange rate calculations.
- Add exchange rate fees.
Make the limits on the size of V2 requests more strict.
Allow a client-provided identifier in /v3/pay to prevent double-ups.
Rate limit failed login attempts (on both API endpoints and the admin pages).
Add /v3/regenerate_token. To ensure atomicity, lurkcoin will accept both tokens until the new token is used.
Don't use big.Float when converting Currency objects from strings.
Don't escape HTML tags in the returned JSON (possibly).
Add a way to request account creation and webhook URLs.
Add PBKDF2 for admin pages password hashes.
Federation.