add error handling and more tests

src/middleware/errorHandler.js

@@ -0,0 +1,36 @@
+const { normalizeError, isTrustedError } = require('../utils/errors');
+
+module.exports = function createErrorMiddleware({ logger = console } = {}) {
+    return function errorMiddleware(err, req, res, next) { // eslint-disable-line no-unused-vars
+        const normalized = normalizeError(err);
+        const status = normalized.statusCode || 500;
+        const response = {
+            error: normalized.code || 'INTERNAL_ERROR',
+            message: normalized.safeMessage || 'An unexpected error occurred.'
+        };
+
+        if (normalized.details) {
+            response.details = normalized.details;
+        }
+
+        if (logger && typeof logger.error === 'function') {
+            const logPayload = {
+                message: normalized.message,
+                code: normalized.code,
+                status,
+                path: req.path,
+                method: req.method,
+                trusted: isTrustedError(normalized)
+            };
+            if (normalized.details) {
+                logPayload.details = normalized.details;
+            }
+            if (normalized.cause) {
+                logPayload.cause = normalized.cause?.message || normalized.cause;
+            }
+            logger.error('Request failed', logPayload);
+        }
+
+        res.status(status).json(response);
+    };
+};