Add initial metrics for Prometheus (#18)

* Add metrics for Prometheus

prover_client/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "prover_client"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+# TODO: workspace?
+tokio = { version = "1", features = ["macros", "rt-multi-thread"] }
+# TODO: workspace?
+tonic = "0.13.1"
+prost = "0.13"
+alloy.workspace = true
+
+[build-dependencies]
+tonic-build = "*"

prover_client/build.rs

@@ -0,0 +1,12 @@
+use std::env;
+use std::path::PathBuf;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
+    tonic_build::configure()
+        .file_descriptor_set_path(out_dir.join("prover_descriptor.bin"))
+        .compile_protos(&["../proto/net/vac/prover/prover.proto"], &["../proto"])
+        .unwrap();
+
+    Ok(())
+}

prover_client/src/main.rs

@@ -0,0 +1,40 @@
+use alloy::primitives::Address;
+use std::str::FromStr;
+use tonic::Response;
+
+pub mod prover_proto {
+
+    // Include generated code (see build.rs)
+    tonic::include_proto!("prover");
+}
+
+use prover_proto::{
+    Address as GrpcAddress, RegisterUserReply, RegisterUserRequest,
+    // RegistrationStatus,
+    rln_prover_client::RlnProverClient,
+};
+
+#[tokio::main]
+async fn main() {
+    // FIXME: clap
+    let url = "http://127.0.0.1:42942";
+    let addr = "0xb20a608c624Ca5003905aA834De7156C68b2E1d0";
+
+    let addr = Address::from_str(addr).unwrap();
+
+    let grpc_addr = GrpcAddress {
+        value: addr.to_vec(),
+    };
+
+    let mut client = RlnProverClient::connect(url).await.unwrap();
+    let request_0 = RegisterUserRequest {
+        user: Some(grpc_addr),
+    };
+    let request = tonic::Request::new(request_0);
+    let response: Response<RegisterUserReply> = client.register_user(request).await.unwrap();
+
+    println!(
+        "RegisterUSerReply status: {:?}",
+        response.into_inner().status
+    );
+}