PluginName defines the name for a notifier plugin.

Handshake is a common handshake that is shared by plugin and host.

PluginMap is the map of plugins we can dispense.

GRPCClient is an implementation of Authenticator interface that talks over RPC.

GRPCServer defines the gRPC server that GRPCClient talks to.

Plugin defines the implementation to serve/connect to an authe plugin.

Authenticator defines the interface for authentication plugins.