Refactor 'uploadFromUrl' to base storage implementation

Add safety around using fetch implementation

server/utils/fetch.ts

@@ -0,0 +1,28 @@
+/* eslint-disable no-restricted-imports */
+import fetchWithProxy from "fetch-with-proxy";
+import nodeFetch, { RequestInit, Response } from "node-fetch";
+import { useAgent } from "request-filtering-agent";
+import env from "@server/env";
+
+/**
+ * Wrapper around fetch that uses the request-filtering-agent in cloud hosted
+ * environments to filter malicious requests, and the fetch-with-proxy library
+ * in self-hosted environments to allow for request from behind a proxy.
+ *
+ * @param url The url to fetch
+ * @param init The fetch init object
+ * @returns The response
+ */
+export default function fetch(
+  url: string,
+  init?: RequestInit
+): Promise<Response> {
+  // In self-hosted, webhooks support proxying and are also allowed to connect
+  // to internal services, so use fetchWithProxy without the filtering agent.
+  const fetch = env.isCloudHosted() ? nodeFetch : fetchWithProxy;
+
+  return fetch(url, {
+    ...init,
+    agent: env.isCloudHosted() ? useAgent(url) : undefined,
+  });
+}