ErrorEncoder is a go kit style http error encoder.

IPToGRPCContext is a grpctransport.ServerRequestFunc that put client ip to context, under contract.IpKey.

IPToHTTPContext is a httptransport.RequestFun that put client ip to context, under contract.IpKey.

RequestURLToHTTPContext adds path information to the context.

TransportToGRPCContext adds path and transport information to the context.

TransportToHTTPContext adds transport information to the context.