refactor widget api design

this passes all widget API calls through the backend, with a pluggable design and reusable API handlers

src/utils/proxies/nzbget.js

@@ -0,0 +1,39 @@
+import { JSONRPCClient } from "json-rpc-2.0";
+import { getServiceWidget } from "utils/service-helpers";
+
+export default async function nzbgetProxyHandler(req, res) {
+  const { group, service, endpoint } = req.query;
+
+  if (group && service) {
+    const widget = await getServiceWidget(group, service);
+
+    if (widget) {
+      const constructedUrl = new URL(widget.url);
+      constructedUrl.pathname = "jsonrpc";
+
+      const authorization = Buffer.from(`${widget.username}:${widget.password}`).toString("base64");
+
+      const client = new JSONRPCClient((jsonRPCRequest) =>
+        fetch(constructedUrl.toString(), {
+          method: "POST",
+          headers: {
+            "content-type": "application/json",
+            authorization: `Basic ${authorization}`,
+          },
+          body: JSON.stringify(jsonRPCRequest),
+        }).then(async (response) => {
+          if (response.status === 200) {
+            const jsonRPCResponse = await response.json();
+            return client.receive(jsonRPCResponse);
+          } else if (jsonRPCRequest.id !== undefined) {
+            return Promise.reject(new Error(response.statusText));
+          }
+        })
+      );
+
+      return res.send(await client.request(endpoint));
+    }
+  }
+
+  return res.status(400).json({ error: "Invalid proxy service type" });
+}