fix user agent assign priority

Author: nleush

lib/utils.js

@@ -111,8 +111,7 @@ export function prepareRequestOptions(request_options, options) {
             }
 
             request_options.headers = request_options.headers || {};
-            request_options.headers['User-Agent'] = options?.user_agent || CONFIG.USER_AGENT;
-
+            
             if (CONFIG.PROXY || options?.proxy) {
 
                 var proxy = options?.proxy || getCustomProxyForUri(uri, options);
@@ -155,6 +154,14 @@ export function prepareRequestOptions(request_options, options) {
                 }
             }
 
+            if (options?.user_agent) {
+                // Let `options.user_agent` be prioritized over `proxy.user_agent`.
+                request_options.headers['User-Agent'] = options?.user_agent;
+            } else if (!request_options.headers['User-Agent']) {
+                // ...otherwise use default user agent.
+                request_options.headers['User-Agent'] = CONFIG.USER_AGENT;
+            }
+
             // Add user agent extension to default agent if avaliable.
             if (options?.getProviderOptions 
                 && (options.getProviderOptions('app.name') || options.getProviderOptions('app.ua_extension'))