Render hint — whether to display as a checkbox or a switch toggle.
Validation error message shown when required is true and value is false.
OptionalrichContent?: RichContentOptional rich content with template text and named link replacements.
Current checked state (mutable — set via next()).
Corresponds to the native BOOLEAN inputType / SINGLE_CHECKBOX server type
and extends BaseCollector. errorMessage is the native display
message for a required unchecked field.
Single checkbox or toggle collector.