Support passing protobuf in text format

[bluecmd]

Hi,

I'm using grpcurl as a library in a client CLI application. Since writing JSON lacks a bit of user friendliness, I would prefer to use the protobuf text format instead.

Compare:

grpcurl -d '{"fan": 0, "mode": "FAN_MODE_PERCENTAGE", "percentage": 50}' -plaintext 127.0.0.1:80 bmc.ManagementService.SetFan

with:

grpcurl -d 'fan: 0, mode: FAN_MODE_PERCENTAGE, percentage: 50' -plaintext 127.0.0.1:80 bmc.ManagementService.SetFan

or as it will be in the client I'm writing:

ubmcctl SetFan fan: 0, mode: FAN_MODE_PERCENTAGE, percentage: 50

Looking at the code I don't see any clear way of making this happen without breaking the interface, except for allowing JSON / Text format interchangeably. Which may be a feature, but could also create some confusion.

Thanks for your consideration

[bluecmd]

Ping @jhump, you seem to be the most active maintainer - do you have any suggestions here? I'd love to contribute a patch if needed, but not sure how you folks would like this done (if at all that is).

[jhump]

@bluecmd, sorry for the lack of response. I think I missed this in my inbox when you originally filed it.

I've started on a branch to address it (#54), but it's not ready to merge yet. I'll play around with it a little more, and add some new tests. After that, I think it will be ready to go.

[bluecmd]

Great! Thanks :)