Framework Layer on top of Tonic

## Feature Request

Following this issue: https://github.com/hyperium/tonic/issues/886, i came with this code:

```rust
use hyper::{Body, Request, Response};
use std::convert::Infallible;
use tonic::body::BoxBody;
use tonic::transport::NamedService;
use tonic::transport::Server as TonicServer;
use tower::Service;

pub struct FRPCServer
where
S: Service, Response = Response, Error = Infallible>
+ NamedService
+ Clone
+ Send
+ 'static,
S::Future: Send + 'static,
{
grpc_services: Vec>,
grpc_reflection_services: Vec<&'static [u8]>,
}

impl FRPCServer
where
S: Service, Response = Response, Error = Infallible>
+ NamedService
+ Clone
+ Send
+ 'static,
S::Future: Send + 'static,
{
pub fn new() -> Self {
FRPCServer {
// grpc_server: TonicServer::builder(),
grpc_services: Vec::new(),
grpc_reflection_services: Vec::new(),
}
}

pub fn add_service(&mut self, service: S, reflection: Option<&'static [u8]>) -> &mut Self {
self.grpc_services.push(Box::new(service));

if reflection.is_some() {
self.grpc_reflection_services.push(reflection.unwrap());
}

self
}

pub async fn listen(self) -> Result<(), Box> {
let addr = "127.0.0.1:5051".parse().unwrap();

let mut server = TonicServer::builder();

let mut services = self.grpc_services;
let first_service = services.remove(0);

let mut router = server.add_service(*first_service.clone());
for service in services {
router = router.add_service(*service.clone());
}

// TODO: if enabled
let mut reflection_service = tonic_reflection::server::Builder::configure();
for reflection in self.grpc_reflection_services {
reflection_service =
reflection_service.register_encoded_file_descriptor_set(reflection.clone())
}

let reflection_service_build = reflection_service.build().unwrap();

router
.add_service(reflection_service_build)
.serve(addr)
.await?;

Ok(())
}
}
```

But i am stuck with the type of S when i want to use it like:
```rust
server.add_service(account_service, None);
server.add_service(notification_service, None);
```

I found an `mismatched types expected struct ` error because `notification_service` is not `account_service`.
It will be really cool if someone can help me with that.

thanks guys.