feat: harden trading SDK examples

examples/middleware_system/src/main.rs

@@ -10,7 +10,7 @@ use sol_trade_sdk::{
     SolanaTrade, TradeTokenType,
 };
 use solana_commitment_config::CommitmentConfig;
-use solana_sdk::{instruction::Instruction, pubkey::Pubkey, signature::Keypair};
+use solana_sdk::{instruction::Instruction, pubkey::Pubkey};
 use std::{str::FromStr, sync::Arc};
 
 #[tokio::main]
@@ -59,7 +59,7 @@ impl InstructionMiddleware for CustomMiddleware {
 /// Initializes a new SolanaTrade client with configuration
 async fn create_solana_trade_client() -> AnyResult<SolanaTrade> {
     println!("🚀 Initializing SolanaTrade client...");
-    let payer = Keypair::from_base58_string("use_your_payer_keypair_here");
+    let payer = sol_trade_sdk::common::keypair::load_keypair_from_env("PRIVATE_KEY")?;
     let rpc_url = "https://api.mainnet-beta.solana.com".to_string();
     let commitment = CommitmentConfig::confirmed();
     let swqos_configs: Vec<SwqosConfig> = vec![SwqosConfig::Default(rpc_url.clone())];