Help: Form Repeater -> Make Values Selectable Only Once

Repeater::make('translations')
    ->relationship('translations')
    ->default(function () {
        return [
            ['locale' => 'en'],
            ['locale' => 'de'],
        ];
    })
    ->schema([
        ToggleButtons::make('locale')
            ->label('Language')
            ->options([
                'en' => 'English',
                'de' => 'German',
            ])
            ->default('en')
            ->required()
            ->inline()
            ->afterStateUpdated(fn (callable $get, $set) => self::updateDisabledLocales($get, $set)),
        TextInput::make('course_title')
            ->label('Course Title')
            ->required()
            ->placeholder('Course Title'),
        Textarea::make('course_excerpt')
            ->label('Course Excerpt')
            ->placeholder('The course excerpt is a short description of the course.'),
        Textarea::make('course_description')
            ->label('Course Description')
            ->placeholder('The course description is a detailed overview of the course.'),
    ])
    ->maxItems(2)
    ->columnSpan('full'),