fix(getIdFromHeaders): Return undefined if not available (#6)

src/libs/id-from-header.ts

@@ -1,29 +1,28 @@
 /**
  * Get ID from `location` header
- * 
+ *
  * This function is used to get the ID resources
  * created in Folio (where you are redirected
  * afterwards).
- * 
+ *
  * @example
  * ```typescript
  * import { getIDFromHeaders } from 'fiken';
- * 
+ *
  * ...
- * 
+ *
  * const res = await fiken.createBankAccountRaw({
  *  ...
  * });
- * 
+ *
  * const id = getIDFromHeaders(res.raw);
  * ```
  */
-export function getIDFromHeaders(resp: Response): string {
-    const loc = resp.headers.get('location');
-    if (!loc) {
-        throw new Error('location header was not found');
-    }
+export function getIDFromHeaders(resp: Response): string | undefined {
+  if (!resp.headers) return;
+  const loc = resp.headers.get('location');
+  if (!loc) return;
 
-    const url = loc.split('/');
-    return url.pop();    
-}
+  const url = loc.split('/');
+  return url.pop();
+}