Return correct HTTP status code on gRPC error #1
Description
Currently, a 500 status code is returned no matter the cause of the error. The API should respond with an appropriate HTTP status code for the error.
An example mapping of gRPC errors -> HTTP status:
https://github.com/GoogleCloudPlatform/google-cloud-node/blob/525fb0fc1a7ad064b75050bfc03455508cf0dba5/packages/common/src/grpc-service.js#L50-L135
An example of gRPC response handler:
https://github.com/GoogleCloudPlatform/google-cloud-node/blob/525fb0fc1a7ad064b75050bfc03455508cf0dba5/packages/common/src/grpc-service.js#L564