Optional fallbackComposition fallback text.
The service will render this text instead of the notification body section if there are no compatible compositions found in the template.
(E.g. All of the compositions in the template declare a greater minimum Template API version than the version supported by the running service instance.)
A list of template compositions.
You can include multiple compositions with different minimum Template API version to create fallback compositions and support the earlier versions of Notification Center (Starting from the Template API version 1).
The service will search for the composition with the version number matching the Template API version it is supporting. If this doesn't exist, the service will then select the composition with the nearest version number smaller than the Template API version it is supporting and render the notification card with that composition.