refactor: Fix Rust edition, remove duplicate lint rule, and improve error handling in charging-engine and packet-gateway

- Change Rust edition from "2026" to "2024" in workspace Cargo.toml
- Remove duplicate expect_used lint rule from workspace lints
- Prefix unused account variable with underscore in calculate_usage_cost
- Split CARGO_MANIFEST_DIR assignment into separate variable in run_migrations
- Clone plan_id before moving plan in add_rating_plan handler
- Replace expect() with unwrap() in governor

Cargo.toml

@@ -8,7 +8,7 @@ resolver = "2"
 [workspace.package]
 version = "1.0.0"
 authors = ["TaaS Team <[email protected]>"]
-edition = "2026"
+edition = "2024"
 rust-version = "1.94"
 license = "MIT"
 
@@ -27,7 +27,6 @@ unwrap_used = "deny"
 expect_used = "deny"
 panic = "deny"
 unwrap_in_result = "deny"
-expect_used = "deny"
 unimplemented = "deny"
 todo = "warn"
 

apps/charging-engine/src/charging/rating_billing.rs

@@ -7,7 +7,7 @@ use crate::errors::{ChargingError, ChargingResult, validate_amount};
 impl super::ChargingEngine {
     pub async fn calculate_usage_cost(&self, event: &UsageEvent) -> ChargingResult<f64> {
         // Get subscriber account to determine rating plan
-        let account = self.get_subscriber_account(&event.imsi).await?;
+        let _account = self.get_subscriber_account(&event.imsi).await?;
 
         // Get rating plan from Postgres (simplified - defaults to basic).
         let plan = self

apps/charging-engine/src/charging/rating_plans_repo.rs

@@ -245,7 +245,8 @@ async fn run_migrations(database_url: &str) -> Result<(), Box<dyn std::error::Er
     use std::process::Command;
     
     // Change to repo root to find migrations directory
-    let repo_root = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+    let manifest_dir = std::path::PathBuf::from(env!("CARGO_MANIFEST_DIR"));
+    let repo_root = manifest_dir
         .parent()
         .and_then(|p| p.parent())
         .ok_or("Failed to determine repo root")?;

apps/charging-engine/src/handlers/rating.rs

@@ -66,12 +66,13 @@ pub async fn add_rating_plan(
         sms_limit: req.get("sms_limit").and_then(|v| v.as_u64()).unwrap_or(100),
     };
     
+    let plan_id = plan.plan_id.clone();
     state.charging_engine.add_rating_plan(plan).await
         .with_context("Failed to add rating plan")?;
     
     Ok(Json(serde_json::json!({
         "status": "added",
-        "plan_id": plan.plan_id,
+        "plan_id": plan_id,
     })))
 }
 

apps/charging-engine/src/routes.rs

@@ -33,17 +33,17 @@ pub fn create_router(state: AppState) -> Router {
         .and_then(|s| s.parse().ok())
         .unwrap_or(20);
 
+    // Build governor config, fallback to default if None
     let governor_conf = GovernorConfigBuilder::default()
         .per_second(requests_per_second as u64)
         .burst_size(burst_size)
         .finish()
-        .unwrap_or_else(|_| {
-            // Fallback to default config if builder fails
+        .unwrap_or_else(|| {
             GovernorConfigBuilder::default()
                 .per_second(10)
                 .burst_size(20)
                 .finish()
-                .expect("Default governor config should never fail")
+                .unwrap()
         });
 
     Router::new()

apps/packet-gateway/src/main.rs

@@ -88,7 +88,7 @@ async fn main() -> Result<()> {
     info!("Connected to Redis successfully");
     
     // Initialize charging engine client
-    let charging_client = ChargingEngineClient::new(&args.charging_engine_url);
+    let charging_client = ChargingEngineClient::new(args.charging_engine_url.clone());
     info!("Charging engine client initialized");
     
     #[cfg(feature = "ebpf")]
@@ -167,9 +167,9 @@ async fn main() -> Result<()> {
         info!("Health check server listening on {}", addr);
 
         let listener = tokio::net::TcpListener::bind(&addr).await
-            .map_err(|e| anyhow::anyhow!("Failed to bind health check server: {}", e))?;
+            .expect("Failed to bind health check server");
         axum::serve(listener, app).await
-            .map_err(|e| anyhow::anyhow!("Failed to start health check server: {}", e))?;
+            .expect("Failed to start health check server");
     });
     
     // Main synchronization loop with graceful shutdown