Reuse a single WebClient instance in HttpBuildCacheProvider

A new WebClient was being constructed on every call to
_makeHttpCoreRequestAsync. Since the provider never configures any
WebClient instance state, a single class member suffices.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: iclanton

rush-plugins/rush-http-build-cache-plugin/src/HttpBuildCacheProvider.ts

@@ -73,6 +73,7 @@ export class HttpBuildCacheProvider implements ICloudBuildCacheProvider {
   private readonly _cacheKeyPrefix: string;
   private readonly _tokenHandler: IHttpBuildCacheTokenHandler | undefined;
   private readonly _minHttpRetryDelayMs: number;
+  private readonly _webClient: WebClient = new WebClient();
   private __credentialCacheId: string | undefined;
 
   public get isCacheWriteAllowed(): boolean {
@@ -373,7 +374,6 @@ export class HttpBuildCacheProvider implements ICloudBuildCacheProvider {
 
     terminal.writeDebugLine(`[http-build-cache] request: ${method} ${url} ${bodyLength} bytes`);
 
-    const webClient: WebClient = new WebClient();
     const fetchOptions: IGetFetchOptions | IFetchOptionsWithBody = {
       verb: method,
       headers: headers,
@@ -383,8 +383,8 @@ export class HttpBuildCacheProvider implements ICloudBuildCacheProvider {
     };
 
     const response: IWebClientResponse | IWebClientStreamResponse = stream
-      ? await webClient.fetchStreamAsync(url, fetchOptions)
-      : await webClient.fetchAsync(url, fetchOptions);
+      ? await this._webClient.fetchStreamAsync(url, fetchOptions)
+      : await this._webClient.fetchAsync(url, fetchOptions);
 
     if (!response.ok) {
       // Drain the response body on stream responses so the connection can be reused