Packaging with Conan. Question about proto files

[Javier G. Sogo]

Hi!

We have been packaging `grpc` and `google-cloud-platform` libraries using Conan for a few weeks now (using CMake build-system files), but some users report about failures (in GCP pubsub). We feel like it is related to old proto files being used in the library, either in `grpc` or `gcp` one, so we are working in the dependency tree revisiting the build process.

I've found that gRPC uses some proto files from other repositories, like https://github.com/grpc/grpc-proto and https://github.com/googleapis/googleapis, is it ok to consider these repositories as dependencies and use the files from there instead of the ones vendored in the `grpc` repository? Basically, before starting the build process, Conan can retrieve the content of `googleapis` and `grpc-proto` and copy it to the proper directories into `grpc` codebase.

Is this a _good approach_? Do these repositories contain always latest/canonical version of these protos? Are there more repositories containing `proto` files that we should consider? 

Thanks for your help.

PS.- Once `grpc` is ready, I will jump to `gcp` and probably ask the same question in their forum. I assume it is important (required?) that both libraries use the same version of `googleapis` and `grpc-proto`. This is something that Conan can enforce.
PS1.- Here it is link to the pull-request where the Conan recipe starts to use packaged `googleapis`: https://github.com/conan-io/conan-center-index/pull/11542