getFavoriteById
Retrieves a favorite by its unique ID.
This method searches the list of favorites for an entry that matches the provided favoriteId. If a matching favorite is found, the corresponding IRainbowFavorite object is returned. Otherwise, the function returns null if no favorite with the specified ID exists.
Return
The IRainbowFavorite object corresponding to the given ID, or null if not found.
Parameters
favoriteId
The unique ID of the favorite to retrieve.