feat(dimentorin): Midtrans payment provider (sandbox VA + QRIS)

- Env: MIDTRANS_MERCHANT_ID / CLIENT_KEY / SERVER_KEY (masked in Debug)
- midtrans_provider: Core API v2/charge for bank_transfer (VA BCA) and qris (gopay)
- PaymentServiceImpl: when MIDTRANS_MERCHANT_ID set -> provider=midtrans, external_ref = real VA number / QR string; falls back to manual refs otherwise
- SMTP: Google app password working (send-otp 200, OTP stored)
- E2E verified (sandbox): VA externalRef=47329093597744219189188, QRIS qr_string EMVCo, confirm->paid
- Credentials stored in BWS (dimentorin_midtrans_*, dimentorin_smtp_*)

imphnen-dimentorin/src/payments/application/payment_service.rs

@@ -75,7 +75,37 @@ impl PaymentService for PaymentServiceImpl {
 		let rate = mentor.mentoring_rate.unwrap_or(50_000.0).round() as i64;
 		let total = rate + SERVICE_FEE;
 		let method = cmd.method.clone();
-		let provider = "manual".to_string(); // swap to midtrans/xendit later
+		// Use Midtrans when credentials are configured; fall back to manual refs.
+		let midtrans = imphnen_libs::environment::ENV.midtrans_merchant_id.clone();
+		let (provider, external_ref) = if !midtrans.is_empty() {
+			let server_key = imphnen_libs::environment::ENV.midtrans_server_key.clone();
+			let order_id = format!("DM-{}", Uuid::new_v4());
+			match method.as_str() {
+				"va" => {
+					let va =
+						crate::payments::application::midtrans_provider::create_va_charge(
+							&order_id,
+							total,
+							"bca",
+							&server_key,
+						)
+						.await?;
+					("midtrans".to_string(), Some(va))
+				}
+				"qris" => {
+					let qr = crate::payments::application::midtrans_provider::create_qris_charge(
+						&order_id,
+						total,
+						&server_key,
+					)
+					.await?;
+					("midtrans".to_string(), Some(qr))
+				}
+				_ => ("manual".to_string(), Some(generate_external_ref(&method, session_id))),
+			}
+		} else {
+			("manual".to_string(), Some(generate_external_ref(&method, session_id)))
+		};
 		let expires_at = Utc::now() + Duration::hours(24);
 
 		let payment = PaymentEntity {
@@ -89,7 +119,7 @@ impl PaymentService for PaymentServiceImpl {
 			method: method.clone(),
 			provider,
 			status: "pending".into(),
-			external_ref: Some(generate_external_ref(&method, session_id)),
+			external_ref,
 			expires_at,
 			created_at: Utc::now(),
 			paid_at: None,