EncodeLevel maps the internal Zap log level to the appropriate Stackdriver level.

GRPCCodeToLevel is the mapping of gRPC return codes and interceptor log level.

GRPCZapLogger returns *zap.Logger from salt/log.Logger.

RFC3339NanoTimeEncoder serializes a time.Time to an RFC3339Nano-formatted string with nanoseconds precision.

ServiceContext adds the correct service information adding the log line It is a required field if an error needs to be reported.

encoderConfig is the default encoder configuration, slightly tweaked to use the correct fields for Stackdriver to parse them.