[WC-3452] Add pusher module to the repo

[r0b1n]

This adds pusher module to the repo, has old widget as an asses to copy into the module.

[github-actions]

AI Code Review

🔶 Changes requested — one or more medium-severity items must be addressed

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What was reviewed

File	Change
packages/pluggableWidgets/pusher-web/src/Pusher.tsx	Refactored from single event handler to eventHandlers[] list
packages/pluggableWidgets/pusher-web/src/Pusher.xml	Replaced notifyActionName/notifyEventAction with eventHandlers object list
packages/pluggableWidgets/pusher-web/src/Pusher.editorConfig.ts	Added check() for duplicate names; updated getCaption
packages/pluggableWidgets/pusher-web/src/utils/PusherListener.ts	Refactored to bind_global + eventHandlersMap; channel-only resubscription
packages/pluggableWidgets/pusher-web/src/utils/getChannelName.ts	Removed as any cast — type fix
packages/pluggableWidgets/pusher-web/src/__tests__/Pusher.spec.tsx	Placeholder only
packages/pluggableWidgets/pusher-web/typings/PusherProps.d.ts	Updated types to match new XML
packages/pluggableWidgets/pusher-web/CHANGELOG.md	Not updated for this change
packages/modules/pusher/	New module package (scripts, package.json, CHANGELOG, LICENSE)

Skipped (out of scope): pnpm-lock.yaml, *.png

⚠️ CI checks could not be retrieved (command required approval). Please verify CI is green before merging.

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Findings

🔶 Medium — pusher-web CHANGELOG not updated for breaking API change

File: packages/pluggableWidgets/pusher-web/CHANGELOG.md
Problem: The existing Unreleased entry only says "Initial widget scaffolding". This PR replaces the entire public API (notifyActionName + notifyEventAction → eventHandlers[]), which is a breaking change for any existing users of this widget. The CHANGELOG must be updated so the module CHANGELOG at packages/modules/pusher/CHANGELOG.md correctly documents what changed in the bundled widget.
Fix:

## [Unreleased]

### Changed

- Replaced single `notifyActionName`/`notifyEventAction` properties with a configurable
  `eventHandlers` list, allowing multiple Pusher events to be bound to separate client actions.

### Added

- Design-time validation: Studio Pro now reports an error when duplicate action names are configured.

Run pnpm -w changelog to add the entry interactively.

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🔶 Medium — Unit tests are a stub; changed behaviour has no coverage

File: packages/pluggableWidgets/pusher-web/src/__tests__/Pusher.spec.tsx
Problem: The spec file contains only expect(true).toBe(true) with a TODO comment. The PR introduces non-trivial logic: multi-handler subscription, deduplicate-action-name validation, the bind_global dispatch path, and the channel-stable / handler-update split in PusherListener. None of this is exercised by any test.
Fix: Replace the placeholder with at minimum:

• PusherListener: subscribe builds handler map; calling with same channel updates map without resubscribing; unsubscribe clears state.
• Pusher component: no subscription rendered when eventHandlers is empty; executeAction is called on the matching handler when an event fires.
• Use @mendix/widget-plugin-test-utils builders (new EditableValueBuilder, actionValue()) instead of manual mock objects.

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⚠️ Low — objectSource.status not checked before reading .value

File: packages/pluggableWidgets/pusher-web/src/utils/getChannelName.ts line 4
Note: objectSource.value is read without first checking objectSource.status. Mendix convention is to check .status === "available" before reading .value to avoid acting on stale data. The function handles undefined gracefully (returns undefined → no subscription), so there is no crash risk, but a loading datasource is silently treated identically to an unavailable one.

export function getChannelName(objectSource: DynamicValue<ObjectItem>): string | undefined {
    if (objectSource.status !== "available") {
        return undefined;
    }
    const object = objectSource.value;
    // ...
}

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⚠️ Low — eventHandlers array reference in useMemo deps may cause subscription churn

File: packages/pluggableWidgets/pusher-web/src/Pusher.tsx line 45
Note: eventHandlers (a Mendix object isList prop) is listed as a useMemo dependency. If the Mendix runtime passes a new array reference on each render (which is possible for list-type props), subscription will be a new object every render, causing the subscription useEffect to unsubscribe and resubscribe on every render. Because PusherListener.subscribe guards against channel re-subscription, the Pusher connection won't bounce, but the React cleanup/effect cycle will still fire unnecessarily.

If this becomes a problem in practice, stabilise subscription by computing only when the serialised handler list changes:

const handlersKey = eventHandlers.map(h => `${h.actionName}`).join(",");
const subscription = useMemo(() => {
    // ...
}, [channelName, handlersKey, handleError]);

The action callbacks themselves can be re-captured from eventHandlers inside the subscription via a ref if needed.

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Positives

• PusherListener.subscribe only resubscribes when channelName changes; handler-only changes update the map without touching the Pusher connection — this is the right optimisation.
• bind_global + eventHandlersMap is a clean pattern that avoids re-binding Pusher channel events on every React render.
• check() in editorConfig.ts gives developers immediate duplicate-name feedback in Studio Pro at design time — a good UX addition.
• Proper AbortController pattern in usePusherSubscribe correctly handles the async-init-then-unmount race.
• Removing the as any cast in getChannelName is the right fix now that the typings correctly reflect DynamicValue<ObjectItem>.
• Module package scaffolding (build.ts, push-update.ts, release.ts) follows the patterns established by other modules in the repo.