reflect error message on client side when there is an error merging calendars

script.js

@@ -41,14 +41,19 @@ const form = document.getElementById('merge-form');
                 },
                 body: JSON.stringify({ calendars: calendarsData })
             })
-            .then((response) => response.json())
+            .then((response) => {
+                if (!response.ok) {
+                    return response.json().then(err => { throw err; });
+                }
+                return response.json();
+            })        
             .then((data) => {
                 result.innerHTML = `Merged calendar URL: <a href="${data.url}">${data.url}</a>`;
                 console.log('Links added successfully!');
             })
             .catch((error) => {
-                console.error(error);
-                result.innerHTML = 'Error merging calendars';
+                console.error('Error:', error);
+                result.innerHTML = `Error merging calendars: ${error.message}`
             });
         });