This implements an 'external plugin' model for extending Miniflare with Workers + Services outside of the Workers-SDK repo.

With this change, a user could specify the following configuration in an unsafe binding and have it emulated locally in a Worker simulator as existing plugins do.

{
        // The name of the binding made available to this Worker
        "name": "MY_INTERNAL_BINDING",
        "service": "some-unsafe-service-binding",
        // We expect the '@cloudflare/example-external-plugin' package
        // to expose a plugin with name 'name-of-plugin-exposed-by-plugin'
        // that will provide the service binding for 'account-services-staging'
        "dev": {
          "package": "@cloudflare/example-external-plugin",
          "plugin": "name-of-plugin-exposed-by-plugin"
        },
        "type": "service",
      }

This package would need to expose a module with the following function export:

import {pluginimplementation } from 'plugins/my-plugin-implementation'
export registerMiniflarePlugins() {
   return {
       'name-of-plugin-exposed-by-plugin': pluginImplementation
   }
}

Notably, this can now happen outside of the Workers-SDK repo, which is important for plugins that may have non-public or implementation details that are confidential or restricted for internal Cloudflare usage.

Context:

Internally at Cloudflare, there is a desire to have a more functional local development environment when using "unsafe" bindings that aren't available for public consumption. Examples of internal bindings may include "unsafe" service bindings between internal Worker services or accessing a Quicksilver binding that will never be publicly exposed to customers but is still highly relevant to internal developers.

This MR tries to allow internal developers at Cloudflare to write and publish Miniflare plugins outside of the workers-sdk repo. These plugins can then be published internally and dynamically imported and merged into Miniflare's existing plugin model.

This MR is in rough draft state and definitely needs comments from the Workers ANT team members to help point out inconsistencies or areas for improvement. Particularly, I'd love reviews and help with:

1. Cleaning up the logic of passing unsafe bindings and validating their options in the miniflare.ts file. I believe there's a better, more strongly typed approach here but it will require a bit of thinking.
2. Tests. I am slightly lost on how to best specify and mock these options in the existing Miniflare test structure. ✅
3. Opinions on the approach for specifying unsafe bindings via a dev section in wrangler.jsonc. ✅
4. Improving the documentation for the anatomy of a plugin. It has taken me a while to understand what each individual plugin method should be returning, even after reading CONTRIBUTING.md. For users who struggle with the intracacies of Miniflare and how it interacts with Wrangler, better comments could go a long way in helping folks contribute plugins. ✅

• Tests
  • Tests included - Need a hand with how to best test this!
  • Tests not necessary because:
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: not for public consumption
• Wrangler V3 Backport
  • Wrangler PR:
  • Not necessary because: new features are not backported