Resolve "Configure MongoDB Connection"

Implemented connectDB, as described in #3 (closed); 1st commit introduced the check if connected to DB and make collections, 2nd commit made it fit the requirements and improved the code by adding error handling.

Closes #6 (closed)

mongodb.js

@@ -4,7 +4,7 @@ const mongoose = require('mongoose');
 async function connectDB() {
   try {
     // Connect using the MongoDB URI from environment variables
-    const conn = await mongoose.connect("mongodb://127.0.0.1:27017");
+    const conn = await mongoose.connect(process.env.MONGO_URI || "mongodb://127.0.0.1:27017/todo_app");
     console.log(`MongoDB connected: ${conn.connection.host}`);
 
     // Get the database object from the connection