Which @angular/* package(s) are relevant/related to the feature request?

common

Description

I would like to be able to provide my own implementation of FetchFactory.

Currently the angular codebase already has an internal solution used for testing only:
https://github.com/angular/angular/blob/main/packages/common/http/src/fetch.ts#L339

The use case where this is relevant is with cloudflare workers under the same account and http request between them is forbidden and you can only use it through service binding to directly call the worker's fetch function.

At the moment I'm "forced" to copy paste the whole FetchBackend class to be able to modify the fetch implementation.

Proposed solution

{
  provide: FetchFactory,
  useClass: CustomFetchFactory,
}

Example implementation

export class CustomFetchFactory implements FetchFactory {
  private bindings  = inject<Bindings>(REQUEST_CONTEXT);

  fetch(url: string, init?: RequestInit): Promise<Response> {
    if (this.bindings?.CF_WORKER && url.includes('cf-worker-under-same-account')) {
      return this.bindings.CF_WORKER.fetch(new Request(url, init));
    }

    return globalThis.fetch(url, init);
  }

}

Alternatives considered

none