Block public access for functions [Resource level]

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**Description**
Allow customers to block public access for functions. Block public access will be a function level attribute, and customers can specify whether to block the attachment of new policies that would allow public access and/or restrict access to functions that are currently publicly accessible. These controls will enable you to block new public policies form being attached to a function without impacting functions that are currently publicly accessible.

En este issue de roadmap no se identifican archivos del repositorio, pruebas ni puntos de entrada. Empieza por aclarar los controles a nivel de función para bloquear nuevas políticas públicas y restringir las funciones que actualmente son públicas; se considera terminado cuando se hayan especificado tanto los dos comportamientos solicitados como su interacción.

Escrito por el modelo de indexación a partir del texto del issue.