(feat): rename example-usage to just example

(feat): add the example's web-client dist folder to a gitignore
(fix): format issues
(fix): a lot of duplicate code

example/client/src/main.rs

@@ -0,0 +1,57 @@
+mod auth;
+mod messages;
+
+use std::fs;
+use std::path::Path;
+
+use mtp::client::ClientConfig;
+use mtp::crypto::{KemPublicKey, PublicKeyBundle, SignaturePqPublicKey, SignaturePublicKey};
+
+fn dev_cert_path() -> String {
+    std::env::var("MTP_DEV_CERT").unwrap_or_else(|_| {
+        if Path::new("example/dev-cert/cert.pem").exists() {
+            "example/dev-cert/cert.pem".to_string()
+        } else {
+            "dev-cert/cert.pem".to_string()
+        }
+    })
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let cert_path = dev_cert_path();
+    let cert_pem = fs::read(&cert_path).unwrap_or_else(|e| {
+        panic!(
+            "Missing TLS certificate at {cert_path}: enter the Nix shell first or run the server to generate it: {e}"
+        )
+    });
+    let host_public_key = PublicKeyBundle::new(
+        KemPublicKey::new(
+            fs::read("host_enc_kem_pk.bin")
+                .expect("Missing host_enc_kem_pk.bin: run server first"),
+        ),
+        SignaturePqPublicKey::new(
+            fs::read("host_sig_pq_pk.bin")
+                .expect("Missing host_sig_pq_pk.bin: run server first"),
+        ),
+        SignaturePublicKey::new(
+            fs::read("host_sig_pk.bin").expect("Missing host_sig_pk.bin: run server first"),
+        ),
+    );
+
+    println!("Connecting to 127.0.0.1:8080 ...");
+
+    let config = ClientConfig {
+        url: "https://127.0.0.1:8080".into(),
+        server_cert: Some(cert_pem),
+        client_id: 0,
+    };
+
+    let server_bundle = host_public_key.clone();
+    let (conn, keyring) =
+        auth::connect_or_register(config, host_public_key, "client_keys.json").await?;
+    messages::send_and_receive(&conn, &keyring, &server_bundle).await?;
+
+    println!("\nDone");
+    Ok(())
+}