feat: add NumberSignal basic support

[taefi]

Description

Add basic support for full-stack NumberSignal type to be returned by endpoints as a shared signal instance that supports number value operations. The client-side user code (for now) need to do manual wrapping of the needed metadata about the endpoint method(s) that return shared signal instance(s).

Assuming a simple endpoint returning a NumberSignal instance like this:

import com.vaadin.hilla.signals.NumberSignal;
import com.vaadin.flow.server.auth.AnonymousAllowed;
import com.vaadin.hilla.BrowserCallable;

@AnonymousAllowed
@BrowserCallable
public class SharedCounterService {
    private final NumberSignal counter = new NumberSignal(0);

    public NumberSignal counter() {
        return counter;
    }
}

The needed manually written user code is like this (this will be generated later):

import { NumberSignalQueue } from "@vaadin/hilla-react-signals";
import client_1 from "Frontend/generated/connect-client.default";

export class CounterServiceWrapper {
  static counter() {
    const signalChannel = new NumberSignalChannel('SharedCounterService.counter', client_1);
    return signalChannel.getSignal();
  }
}

Then then usage of this wrapping service in views could be similar to what is described in the related issue:

const counter = CounterServiceWrapper.counter();

export default function NumberSignalView() {
  return (
    <Button onClick={() => counter.value++}>
       Click count: { counter }
    </Button>
  );
}

Fixes #2429

Type of change

• Bugfix
• Feature

Checklist

• I have read the contribution guide: https://vaadin.com/docs/latest/guide/contributing/overview/
• I have added a description following the guideline.
• The issue is created in the corresponding repository and I have referenced it.
• I have added tests to ensure my change is effective and works as intended.
• New and existing tests are passing locally with my change.
• I have performed self-review and corrected misspellings.

Additional for Feature type of change

• Enhancement / new feature was discussed in a corresponding GitHub issue and Acceptance Criteria were created.

[Legioth]

Why is package-lock.json changed without any corresponding change to package.json?

[taefi]

Why is package-lock.json changed without any corresponding change to package.json?

Good catch. That was unintentionally committed/pushed. Reverted.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.53%. Comparing base (fca044b) to head (ce42feb).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2502      +/-   ##
==========================================
- Coverage   92.56%   92.53%   -0.03%     
==========================================
  Files          69       68       -1     
  Lines        2245     2238       -7     
  Branches      590      590              
==========================================
- Hits         2078     2071       -7     
  Misses        120      120              
  Partials       47       47              

Flag	Coverage Δ
unittests	92.53% <ø> (-0.03%)	⬇️

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[sonarcloud]

Quality Gate passed

Issues
7 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[sonarcloud]

Quality Gate passed

Issues
11 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud