Send user agent as tranquil

src/lib.rs

···
         )
         .fallback(async || (
             StatusCode::NOT_IMPLEMENTED,
-            Json(json!({"error": "MethodNotImplemented", "message": "XRPC method not implemented"})),
+            Json(json!({"error": "MethodNotImplemented", "message": "Method not implemented. For app.bsky.* methods, include an atproto-proxy header specifying your AppView."})),
         ));
     let xrpc_service = ServiceBuilder::new()
         .layer(XrpcProxyLayer::new(state.clone()))

src/oauth/client.rs

···
                 .connect_timeout(std::time::Duration::from_secs(10))
                 .pool_max_idle_per_host(10)
                 .pool_idle_timeout(std::time::Duration::from_secs(90))
+                .user_agent("Tranquil-PDS/1.0 (ATProto; +https://tangled.org/lewis.moe/bspds-sandbox)")
                 .build()
                 .unwrap_or_else(|_| Client::new()),
             cache_ttl_secs,
···
             .send()
             .await
             .map_err(|e| {
+                tracing::warn!(client_id = %client_id, error = %e, "Failed to fetch client metadata");
                 OAuthError::InvalidClient(format!("Failed to fetch client metadata: {}", e))
             })?;
         if !response.status().is_success() {
+            tracing::warn!(client_id = %client_id, status = %response.status(), "Failed to fetch client metadata");
             return Err(OAuthError::InvalidClient(format!(
                 "Failed to fetch client metadata: HTTP {}",
                 response.status()