Add Proxy Support for Assistant API Calls in Assistance.ts

[SaturninS]

Describe the problem to be solved

Currently, the Assistance.ts module in app/server/lib handles API calls to external LLM endpoints (e.g., for the Assistant feature). However, these calls do not leverage the existing proxyAgent utility, which limits the flexibility for self-hosted deployments behind proxies.

Describe the solution you would like

Integrate the proxyAgent utility in Assistance.ts to enable proxy support for API calls. This would align the behavior of Assistance.ts with other modules like Requests.ts, Triggers.ts, and WidgetRepository.ts, which already implement proxy support.
Implementation Details
File to update: app/server/lib/Assistance.ts
Import the proxyAgent utility from app/server/lib/ProxyAgent.
Update the fetch implementation in Assistance.ts to include the agent option using proxyAgent.
`import fetch from 'node-fetch';
import { proxyAgent } from './ProxyAgent';

const GRIST_HTTPS_PROXY = process.env.GRIST_HTTPS_PROXY;

export const DEPS = {
fetch: async (url: string, options: any = {}) => {
const agent = GRIST_HTTPS_PROXY ? proxyAgent(new URL(url)) : undefined;
return fetch(url, { ...options, agent });
},
delayTime: 1000,
};
`
The functionality will only activate if the GRIST_HTTPS_PROXY environment variable is set.