fix: Wrap headers with AxiosHeaders to prevent incorrect type being passed

src/interceptor.ts

@@ -70,8 +70,8 @@
   Record<string, string>
 >;
 
 const removeUndefined = (obj: Record<string, any>) => {
   const newObj: Record<string, any> = {};
 
   for (const [key, value] of Object.entries(obj)) {
     if (value !== undefined) {
@@ -94,7 +94,7 @@
  * @param options The options to be used when signing a request
  * @param credentials Credentials to be used to sign the request
  */
 export const aws4Interceptor = <D = any>({
   instance = axios,
   credentials,
   options,
@@ -130,7 +130,8 @@
     }
 
     const { host, pathname, search } = new URL(url);
-    const { data, headers, method } = config;
+    const { data, method } = config;
+    const headers = new AxiosHeaders(config.headers);
 
     const transformRequest = getTransformer(config);
 
@@ -149,7 +150,7 @@
       put,
       patch,
       ...headersToSign
     } = headers as any as InternalAxiosHeaders;
     // Axios type definitions do not match the real shape of this object
 
     const signingOptions: AWS4Request = {
@@ -160,7 +161,7 @@
       service: options?.service,
       signQuery: options?.signQuery,
       body: transformedData,
       headers: removeUndefined(headersToSign) as any,
     };
 
     const resolvedCredentials = await credentialsProvider.getCredentials();