Fix linting errors

src/FetchClient.test.ts

@@ -1,6 +1,5 @@
 import { assert, assertEquals, assertFalse } from "@std/assert";
 import {
-  defaultProvider,
   defaultProvider as provider,
   FetchClient,
   ProblemDetails,

src/FetchClient.ts

@@ -120,6 +120,16 @@ export class FetchClient {
     return this.requestCount > 0;
   }
 
+  /**
+   * Adds one or more middleware functions to the FetchClient's middleware pipeline.
+   * Middleware functions are executed in the order they are added.
+   *
+   * @param mw - The middleware functions to add.
+   */
+  public use(...mw: FetchClientMiddleware[]): void {
+    this.#middleware.push(...mw);
+  }
+
   /**
    * Sends a GET request to the specified URL.
    *

src/FetchClientProvider.ts

@@ -80,10 +80,11 @@ export class FetchClientProvider {
 
   /**
    * Creates a new instance of FetchClient using the current provider.
+   * @param options - The options to use for the new FetchClient instance. Options provided here will override the default options set on the provider.
    * @returns A new instance of FetchClient.
    */
-  public getFetchClient(): FetchClient {
-    return new FetchClient({
+  public getFetchClient(options?: FetchClientOptions): FetchClient {
+    const o = {
       defaultRequestOptions: this.#options.defaultRequestOptions,
       baseUrl: this.#options.baseUrl,
       cache: this.#cache,
@@ -92,7 +93,9 @@ export class FetchClientProvider {
       modelValidator: this.#options.modelValidator,
       accessTokenFunc: this.#options.accessTokenFunc,
       providerCounter: this.#counter,
-    });
+    };
+    options = { ...o, ...options };
+    return new FetchClient(options);
   }
 
   /**