Only save global settings the user has entered

[roborourke]

Fixes #15.

The bug

The Set as global defaults button built its payload from all three block attributes every time:

saveSite( {
	hubspot_embed_portal_id: newPortalId,
	hubspot_embed_region: newRegion,
	hubspot_embed_business_unit_id: newBusinessUnitId || 0,
} );

A blank field in that panel means "inherit the global default shown as the placeholder", but it was still sent — and it broke in two different ways depending on the field:

• Business Unit ID was coerced to 0 by || 0, overwriting a previously stored value with an empty one. This is the wipe described in the issue.
• Portal ID and Region were sent as null. WP_REST_Settings_Controller only deletes an option on null when it has no stored value; once it holds one, it bails out with rest_invalid_stored_value and a 500 — and because it returns on the first offending option, nothing in the request is saved, including the value the user was actually trying to set. (CI confirmed this: my first attempt at the tests used null to reset the options and got The hubspot_embed_portal_id property has an invalid stored value, and cannot be updated to null.)

Region had a third problem: its block attribute defaults to eu1, so promoting any global on a site whose region was na1 sent eu1 over the top of it.

The fix

Track which of the global fields the user actually edited, and build the saveSite payload from only those that hold a value:

• Each global can be saved on its own; the others are not sent at all, so they keep their stored values and the request no longer aborts.
• A blank field is never submitted, so it cannot overwrite a saved global — the placeholder keeps showing the inherited value.
• The button is hidden unless there is something to promote (including after typing into a field and clearing it again).
• Only the overrides that were actually promoted get cleared from the block attributes.

Also fixed the two editor notices, which checked the global portal ID alone and told the user to "enter a Portal ID" even when the block supplied its own — they now fall back the same way render.php does.

Testing

tests/global-settings.spec.js covers the reported sequence and the region case:

• Save a Portal ID alone, then a Business Unit ID alone — both globals survive, and the Portal ID field falls back to showing the saved value as its placeholder.
• Promoting a Portal ID on a site with region = na1 leaves the region alone.
• The save button only appears once a global value is entered.

npm run lint:js and npm run build pass locally. The Playwright suite needs Playground to download WordPress, which is blocked in my sandbox, so these run in CI only.

[github-actions]

Playwright E2E Test Results (PHP 8.4, WP latest)

 17 passed
 2 flaky

Details

 19 tests across 5 suites
 3 minutes, 51 seconds
 b671390

Flaky tests

chromium › form-render.spec.js › HubSpot Form — frontend render › should render form container with correct data attributes
chromium › persist-success.spec.js › HubSpot Form — persist success › should pre-swap the container on repeat visit, stripping the first-submission group