Protobuf encoding used by macaroon-bakery (library)

 This module defines the serialization format of macaroon identifiers
 for macaroons created by the macaroon-bakery. For the most part this
 encoding is considered an internal implementation detail of the
 macaroon-bakery and external applications should not rely on any of the
 details of this encoding being maintained between different bakery versions.
 .
 This is broken out into a separate module as the protobuf implementation
 works in such a way that one cannot have multiple definitions of a
 message in any particular application's dependency tree. This module
 therefore provides a common definition for use by multiple versions of
 the macaroon-bakery to facilitate easier migration in client applications.