Allow docstrings for generated modules about tonic

[LucioFranco]

@sezna Hi! So quick and easy fix is to annotate the overall module with #[allow(missing_docs].

Do you by chance know which module is causing the error? is it the client/server mod?

[sezna]

I haven't actually used the client or the server yet. Right now I'm just generating structs from .proto files. When I run codegen like this:

tonic_build::configure().compile(&["foo.proto"], &["../protocol"]).unwrap()

it generates code like this:

#[allow(non_snake_case, unused_attributes)]
mod foo_MESSAGE {
    extern crate bytes as _bytes;
    extern crate prost as _prost;
    use super::*;
    impl _prost::Message for Foo {
       // ... lots of methods
    }
}
// <-- there is no way for me to put a docstring here
pub mod foo { // missing doc warning happens here
    // ... lots of methods and things
}

I could wrap the import macro with another module and allow missing docs on it for now, but that doesn't seem optimal, because I would like to have doc enforcement on all of my protobuf fields as I currently do.

[LucioFranco]

This sounds like something prost is doing, we add doc comments to all the mods we generate and we just append that to the file that prost generates.

As for wrapping it in a mod I generally tend to do that anyways.

[sezna]

Hm, ok. I will wrap it for now and talk to the prost people about this. Thanks!