Biscuit authentication token

Biscuit is a (in development) authentication token for microservices architectures with the following properties:

distributed authorization: any node could validate the token only with public information
offline delegation: a new, valid token can be created from another one by attenuating its rights, by its holder, without communicating with the issuer or the verifier
capabilities based: authorization in microservices should be tied to rights related to the request, instead of relying to an identity that might not make sense to the verifier
flexible rights managements: the token specifies a pattern based right specification and attenuation syntax taht can map to other rights management systems
small enough to fit anywhere (cookies, etc)

Non goals:

this is not a new authentication protocol. Biscuit tokens can be used as opaque tokens delivered by other systems such as OAuth
revocation: while tokens come with expiration dates, revocation requires external state management