feat: add unpack/2 to Protobuf.Any

[yordis]

Signed-off-by: Yordis Prieto yordis.prieto@gmail.com

Related to #360 and #409 this is the safest way I found to introduce the feature without making such big assumptions that it wouldn't work.

I have done this professionally for a while using https://hex.pm/packages/trogon_typeprovider

defmodule Umbrella.Grpc.TypeProvider do
  use Trogon.TypeProvider, prefix: "type.googleapis.com/"

  register_type "google.rpc.BadRequest", Google.Rpc.BadRequest
  register_type "google.rpc.ErrorInfo", Google.Rpc.ErrorInfo
  register_type "google.rpc.Status", Google.Rpc.Status

  # ... add more
end

Intentionally, I did not make any assumptions around the type_url as far as I can tell, it is not required to be type.googleapis.com/ prefixed.

• What about global type provider?

We could make the type provider module optional and fallback to some Application.compiled_env! or something like that, personally, I rather introduce the feature avoiding global assumptions. We can always add a global function that make such assumption instead.

[yordis]

@whatyouhide here is the follow up work, I did the most safe way I found that would truely work across different projects, which I also tested there.

I did not make assumptions about the prefix because as far as I can tell, we can't, but, correct me here.