makeHttpError: Ensure response headers have lowercase names

ts/textsecure/WebAPI.ts

@@ -638,12 +638,25 @@ function makeHTTPError(
 ) {
   return new HTTPError(message, {
     code: providedCode,
-    headers,
+    headers: makeKeysLowercase(headers),
     response,
     stack,
   });
 }
 
+export function makeKeysLowercase<V>(
+  headers: Record<string, V>
+): Record<string, V> {
+  const keys = Object.keys(headers);
+  const lowerCase: Record<string, V> = Object.create(null);
+
+  keys.forEach(key => {
+    lowerCase[key.toLowerCase()] = headers[key];
+  });
+
+  return lowerCase;
+}
+
 const URL_CALLS = {
   accountExistence: 'v1/accounts/account',
   attachmentUploadForm: 'v4/attachments/form/upload',