feat: extensible section form schema via extendSchemaUsing [3.x]

[ManukMinasyan]

What

Adds an extension point to the Custom Fields section management form.

• SectionForm::extendSchemaUsing(Closure $callback) — register a callback (e.g. from a service provider) that appends to / modifies the section form schema. A single registration covers both the Add and Edit section modals. The callback receives (array $schema, string $entityType), so extensions can be scoped per entity.
• SectionForm::flushSchemaExtensions() — clears registrations (test isolation).
• CustomFieldSectionSettingsData gains a free-form array $extra bag, so arbitrary consumer-defined settings bound under settings.extra.* round-trip through the typed DTO (and through CustomFieldSectionData import/export). The typed DTO silently drops unknown keys, so a bag is required for arbitrary flags to survive hydration.

Why

Applications consuming CustomFields::infolist() need to attach their own per-section metadata — e.g. "render this section as its own tab" — without subclassing the form or patching the vendor.

Usage

// AppServiceProvider::boot()
use Relaticle\CustomFields\Filament\Management\Schemas\SectionForm;
use Filament\Forms\Components\Toggle;

SectionForm::extendSchemaUsing(fn (array $schema, string $entityType): array => [
    ...$schema,
    Toggle::make('settings.extra.render_as_tab')
        ->label('Render as own tab')
        ->visible($entityType === 'contact'),
]);

// read it back
$renderAsTab = $section->settings->extra['render_as_tab'] ?? false;

Test plan

New tests in CustomFieldsSectionManagementTest:

• extension callback receives the section entity type
• a field added via extendSchemaUsing persists into settings.extra on create
• the extra value survives an edit round-trip

Verified locally: full suite 694 passed; Pint, PHPStan, Rector --dry-run, and arch tests all green. (Type coverage sits at 99.4% on 3.x already — pre-existing, in unrelated files.)

Notes

• Additive and backward-compatible: the new DTO property defaults to []; the hook is opt-in.
• No migration — settings is already JSON.