feat(node): add generic requestREST method

This commit introduces a new public method, `requestREST`, to the `LavalinkNode` class.

This utility provides a flexible and centralized way to make arbitrary REST API calls to the connected Lavalink node. It simplifies interactions with custom endpoints or those provided by Lavalink plugins by handling authentication, URL construction, and basic response parsing automatically.

Key features include:
- Support for modifying request options (method, headers, body).
- Automatic handling of authorization headers.
- Optional response parsing as text instead of JSON.
- Built-in request timeout support.

Author: appujet

src/structures/Node.ts

@@ -157,6 +157,60 @@ export class LavalinkNode {
 
         return { response, options: options };
     }
+    
+    /**
+    * Request a REST endpoint on the Lavalink node.
+    * 
+    * @param fullPath The full path of the endpoint to request (e.g. `/youtube/oauth/`)
+    * @param modify A function to modify the request options before sending the request
+    * @param parseAsText If true, the response will be parsed as a string instead of JSON
+    * @returns A promise that resolves to the response data as a JSON object or string if `parseAsText` is true
+    * @throws {Error} If the node is not connected to the Lavalink Server
+    */
+    public async requestREST<T = unknown>(fullPath: string, modify?: ModifyRequest): Promise<T>;
+    public async requestREST(fullPath: string, modify: ModifyRequest | undefined, parseAsText: true): Promise<string>;
+    public async requestREST<T>(
+        fullPath: string,
+        modify?: ModifyRequest,
+        parseAsText?: boolean
+    ): Promise<T | string> {
+        if (!this.connected) {
+            throw new Error("The node is not connected to the Lavalink Server!");
+        }
+
+        const options: RequestInit & { path: string, extraQueryUrlParams?: URLSearchParams } = {
+            path: fullPath.startsWith("/") ? fullPath : `/${fullPath}`,
+            method: "GET",
+            headers: {
+                "Authorization": this.options.authorization
+            },
+            signal: this.options.requestSignalTimeoutMS && this.options.requestSignalTimeoutMS > 0
+                ? AbortSignal.timeout(this.options.requestSignalTimeoutMS)
+                : undefined,
+        };
+
+        modify?.(options);
+
+        const url = new URL(`${this.restAddress}${options.path}`);
+
+        if (options.extraQueryUrlParams?.size) {
+            for (const [k, v] of options.extraQueryUrlParams.entries()) {
+                url.searchParams.append(k, v);
+            }
+        }
+
+        const { ...fetchOptions } = options;
+        const response = await fetch(url.toString(), fetchOptions);
+
+        this.calls++;
+
+        if (["DELETE", "PUT"].includes(options.method)) return undefined as any;
+        if (response.status === 204) return undefined as any;
+        if (response.status === 404) throw new Error(`Request failed: ${options.path}`);
+
+        return parseAsText ? await response.text() : await response.json();
+    }
+
     /**
      * Makes an API call to the Node. Should only be used for manual parsing like for not supported plugins
      * @param endpoint The endpoint that we will make the call to