Allow for custom params passed from RequestOptions to MiddlewareCallbackParams

[sk22]

Description

Example use case: A middleware that adds a configurable timeout, like this: #2527 (comment)

// Timeout middleware
fetchClient.use({
	async onRequest({ request, params: { timeout } }) {
		const signal =
			timeout === Infinity ?
				request.signal
			:	AbortSignal.any([
					request.signal,
					AbortSignal.timeout(typeof timeout === 'number' && timeout >= 0 ? timeout : REQUEST_TIMEOUT),
				]);
		return new Request(request, { signal });
	},
});

Since #2527, the MiddlewareRequestParams are easily augmentable:

declare module 'openapi-fetch' {
	interface MiddlewareRequestParams {
		timeout?: number;
	}
}

so maybe, ParamsOption should somehow do the same.

Proposal

Ergonomically, I'd like to send my request like this

client['/api/takes-a-while'].PUT({ params: { timeout: 120_000 } })

and use the timeout custom param in my middleware, without type assertions or disabling TypeScript for this line.

Alternatively, I could also imagine a custom meta option, like TanStack Query does it: https://tanstack.com/query/latest/docs/framework/react/typescript#typing-meta

client['/api/takes-a-while'].PUT({ meta: { timeout: 120_000 } })

and accessing it from the middleware like this:

// Timeout middleware
fetchClient.use({
	async onRequest({ request, meta: { timeout } }) {
		// ...

Extra

• I’m willing to open a PR (see CONTRIBUTING.md)

[sk22]

A possible workaround, as @Katli95 described, is to pass it directly into the request options: #2527 (comment)

client['/api/takes-a-while'].PUT({ timeout: 120_000 })

TypeScript doesn't complain here, and openapi-fetch assigns the custom property directly to the Request object.
Only thing for users left to do would be to augment the global Request interface:

declare global {
	interface Request {
		timeout?: number;
	}
}

and access the timeout from the request object, like this:

// Timeout middleware
fetchClient.use({
	async onRequest({ request }) {
		const { timeout } = request;

But again, that's a workaround, and it's not particularly pretty.