Pass serve handler arguments to middleware to access req-only data

Summary

In some cases, a user may want to access the incoming request objects in a way that doesn't affect how Inngest should handle the request. For example, in the case of utilizing Cloudflare AI on Cloudflare Workers, an Ai instance is created using the env object passed to the request.

Currently, arguments being passed to the request handler are used only by the serve handler and aren't exposed to the function. Part of the reason for this is that the serve handler is currently entirely separate from creating functions, so typing request arguments would be difficult.

To resolve this in this PR, we instead pass these arguments to middleware, where we can then assess the request arguments and add properties to our function's input. #383 is used as the problem to solve here.

With this PR, #383 would be resolved using the following middleware:

import { Ai } from "@cloudflare/ai";
import { InngestMiddleware } from "inngest";

interface Env {
  // If you set another name in wrangler.toml as the value for 'binding',
  // replace "AI" with the variable name you defined.
  AI: any;
}

export const cloudflareMiddleware = new InngestMiddleware({
  name: "foo",
  init: () => {
    return {
      onFunctionRun: ({ reqArgs }) => {
        const [, env] = reqArgs as [Request, Env];
        const ai = new Ai(env.AI);

        return {
          transformInput: () => {
            return { ctx: { ai } };
          },
        };
      },
    };
  },
});

This would then be used like so:

import { inngest } from "./client";

export default inngest.createFunction(
  { id: "hello-world" },
  { event: "demo/event.sent" },
  async ({ ai }) => {
    // `ai` is typed and can be used directly or within a step
    const response = await ai.run("@cf/meta/llama-2-7b-chat-int8", {
      prompt: "What is the origin of the phrase Hello, World",
    });
  }
);

Checklist

[x] Added a docs PR that references this PR
[x] Added unit/integration tests
[x] Added changesets if applicable

Fixes #383
inngest/website#623

inngest / inngest-js

Pass serve handler arguments to middleware to access req-only data #453

Summary

Checklist

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🦋 Changeset detected