3.13.0

• Add support for custom encode and decode keys (#91). There are now two new callbacks that can be registered: decode_key_loader and encode_key_loader. The decode callback is passed in the unverified JWT claims, and must return a string that will be used to decode and verify the JWT. The encode callback is passed in the identity (as passed in to the create_access_token or create_refresh_token functions) and must return a string that will be used to encode a JWT. If unset, the JWT_SECRET_KEY, JWT_PUBLIC_KEY, or JWT_PRIVATE_KEY will still be used as appropriate.