[Feature]Add grpc.default_authority option for authorization

[jcai]

Is your feature request related to a problem? Please describe.
Some gRPC server use token to identify the current user in the same service port.

Describe the solution you'd like
add grpc.default_authority option to grpc channel

see:
wechaty/puppet-service#78

[huan]

ping @wechaty/java

This authorization method will be added in the future of the standard wechaty puppet service, so please take a look at it and I hope it can be supported soon.

Thank you very much.