Overhaul networkUtils and expand auth

public/js/networkUtils.js

@@ -1,31 +1,31 @@
+// public/js/networkUtils.js
 export function sendRequest(url, method = "GET", data = null, customHeaders = {}) {
   const options = {
     method,
     credentials: 'include',
-    headers: {}
+    headers: { ...customHeaders }
   };
 
-  // Merge custom headers
-  Object.assign(options.headers, customHeaders);
-
-  // If data is provided and is not FormData, assume JSON.
   if (data && !(data instanceof FormData)) {
-    if (!options.headers["Content-Type"]) {
-      options.headers["Content-Type"] = "application/json";
-    }
+    options.headers['Content-Type'] = options.headers['Content-Type'] || 'application/json';
     options.body = JSON.stringify(data);
   } else if (data instanceof FormData) {
     options.body = data;
   }
 
   return fetch(url, options)
-    .then(response => {
-      if (!response.ok) {
-        return response.text().then(text => {
-          throw new Error(`HTTP error ${response.status}: ${text}`);
-        });
+    .then(async res => {
+      const text = await res.text();
+      let payload;
+      try {
+        payload = JSON.parse(text);
+      } catch {
+        payload = text;
       }
-      const clonedResponse = response.clone();
-      return response.json().catch(() => clonedResponse.text());
+      if (!res.ok) {
+        // Reject with the parsed JSON (or raw text) so .catch(error) gets it
+        throw payload;
+      }
+      return payload;
     });
 }