Allow client to be extended with custom-made controllers

[fdionisi]

Check for existing issues

• Completed

Describe the feature

The current client supports the standards EDC contexts, but when working within dataspaces there are likely extensions providing additional functionalities (e.g., BPN validation or Resources Count API).

Would be great if we could reuse EdcConnectorClient plumbing to allow the class to be extended with additional controllers.

If applicable, add text / mockups / screenshots to help present your vision of the feature

There's some TypeScript-related research to be done to make this composition and typing possible (perhaps taking inspiration by Express.js/Koa middleware systems).

The hope is to have a fully typed solution such that:

const client = new EdcConnectorClient.Builder()
  .managementUrl("https://edc.think-it.io/management")
  .build()
  .use("bpnValidator", BpnValidatorController);

await client.bpnValidator.resolve(bpnString);

[ndr-brt]

This feature should be documented