chore: Reorganize examples and interop crates (#180)

* chore: Reorganize examples and interop crates

* fix interop tests

examples/src/authentication/client.rs

@@ -0,0 +1,32 @@
+pub mod pb {
+    tonic::include_proto!("grpc.examples.echo");
+}
+
+use http::header::HeaderValue;
+use pb::{echo_client::EchoClient, EchoRequest};
+use tonic::transport::Channel;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let channel = Channel::from_static("http://[::1]:50051")
+        .intercept_headers(|headers| {
+            headers.insert(
+                "authorization",
+                HeaderValue::from_static("Bearer some-secret-token"),
+            );
+        })
+        .connect()
+        .await?;
+
+    let mut client = EchoClient::new(channel);
+
+    let request = tonic::Request::new(EchoRequest {
+        message: "hello".into(),
+    });
+
+    let response = client.unary_echo(request).await?;
+
+    println!("RESPONSE={:?}", response);
+
+    Ok(())
+}