Embedded JSON in JSONRPC Responses

[mvandeberg]

As a developer interfacing with the Koinos API via JSONRPC, I would like error responses to not contain stringified JSON.

e.g. Koinos Chain can return an error response that looks like this:

{"jsonrpc":"2.0","error":{"code":-32603,"message":"contract does not exist","data":"{\"code\":102}"},"id":1} (koinos/koinos-chain#677)

The problem is the "data":"{\"code\":102}"}. In order to programmatically interact with data, JSON must be parsed again.

We can change the proto error_response to better hold this data.

message error_response {
   string message = 1;
   map<string, google.protobuf.Any> data = 2;
}

Then, in jsonrpc, we can parse data and convert it to a golang map that can be encoded in json.