feat: allow Connector's addresses to be relative URLs

[fdionisi]

Description

Up until now, Addresses were required to include the origin (e.g., https://my.edc.example.com/api/check/health), but it become impractical when we want to implement a UI with proxy on the same origin (e.g., /api/check/health).

This ability allow the URL to be relative, enabling the use case mentioned above.

How to test it

Added a test to ensure failure is coming from the HTTP request, and not from the URL construction. Since relative URLs work only in the browser, I wouldn't know how to test this without bringing in a new e2e setup (e.g., using playwright or cypress)

---

Approach

Rather then constructing the URL via new URL(...) and then adding query parameters to the instance, URL is simply a concatenation of two strings – the "baseUrl" (or relative path) and the resource path), appending at the end the query params added to a newly instance of URLSearchParams:

    const searchParams = new URLSearchParams();
    if (innerRequest.query) {
      Object.entries(innerRequest.query).forEach(([key, value]) => {
        searchParams.append(key, value);
      });
    }

    const url = `${baseUrl}${innerRequest.path}?${searchParams.toString()}`;

[fdionisi]

@ndr-brt not ideal, but this PR also solves an issue with main where new controllers were added which uses JS private fields #inner and #context instead of TS protected ones - my bad in preparing the previous PR.

If you think we should split the work, I'm happy to do so. Otherwise we can get this in, and taking two birds with one stone.

[ndr-brt]

good for me! 🚀