feat: support context-aware empty value preservation

[HugoHSun]

🚥 Resolves CX-1601

🧰 Changes

API Explorer uses empty objects as placeholders for object-shaped array items while the form is being edited. Those placeholders are useful in the UI, but they should not be sent as real values in the request payload.

The first pass added a dedicated option for empty objects inside arrays, but that made the package API more specific than it needed to be. This keeps the existing preserveEmptyObject and preserveEmptyArray options, and lets them accept a context map for root, objectProperty, and arrayItem. Existing boolean usage still works, while callers that need more control can choose exactly where empty values should be preserved.

For API Explorer, this means we can preserve intentional empty object properties while still filtering empty object array-item placeholders out of the payload.

🧬 QA & Testing

Added coverage for context-aware empty object and empty array preservation, including the case where both option maps are used together.

[darrenyong]

should we add an early return for a falsy value of rule just to make it a little more clear?

Suggested change

	function shouldPreserve(rule: PreservationRule | undefined, context: PreservationContext) {
	if (typeof rule === 'boolean') {
	return rule;
	}
	return rule?.[context] ?? false;
	}
	function shouldPreserve(rule: PreservationRule | undefined, context: PreservationContext) {
	if (!rule) return false;
	if (typeof rule === 'boolean') {
	return rule;
	}
	return rule?.[context];
	}