feat: Error handling middleware

feat: Ability to get the db variable from everywhere with getDatabase function
feat: Hello world when getting root url
fix: Now mods model is able to communicate with db
fix: fixed a syntax error in routes/mods.js file which caused sending two responses to the client

src/utils/AppError.js

@@ -0,0 +1,22 @@
+class AppError extends Error {
+    constructor(statusCode, message) {
+        super(message);
+        this.statusCode = statusCode;
+        
+        if (status_code.ToString().startsWith("4")) {
+            this.status = "fail";
+        } else {
+            this.status = "error";
+        }
+    }
+}
+
+exports.tryCatch = (controller) => async (req, res, next) => {
+    try {
+      await controller(req, res, next);
+    } catch(err) {
+      next(err);
+    }
+}
+
+module.exports = AppError;