Added default middleware chain construction note

Author: muthurathinam-m

src/HTTPClientFactory.ts

@@ -40,6 +40,12 @@ export class HTTPClientFactory {
 	 * Creates HTTPClient with default middleware chain
 	 * @param {AuthenticationProvider} authProvider - The authentication provider instance
 	 * @returns A HTTPClient instance
+	 *
+	 * NOTE: These are the things that we need to remember while doing modifications in the below default pipeline.
+	 * 		* HTTPMessageHander should be the last one in the middleware pipeline, because this makes the actual network call of the request
+	 * 		* TelemetryHandler should be the one prior to the last middleware in the chain, because this is the one which actually collects and appends the usage flag and placing this handler 	*		  before making the actual network call ensures that the usage of all features are recorded in the flag.
+	 * 		* The best place for AuthenticationHandler is in the starting of the pipeline, because every other handler might have to work for multiple times for a request but the auth token for
+	 * 		  them will remain same. For example, Retry and Redirect handlers might be working multiple times for a request based on the response but their auth token would remain same.
 	 */
 	public static createWithAuthenticationProvider(authProvider: AuthenticationProvider): HTTPClient {
 		const authenticationHandler = new AuthenticationHandler(authProvider);