// ast_node_view_policy.idl 
MongoExtensionViewPolicy:
   description: Stage-specific rules for view resolution.
   type: string
   values:
      kDefault: "default"
      kCustom: "custom"
      kDisallowed: "disallowed" 

// C API
typedef struct MongoExtensionAggStageASTNodeVTable {
   /**
     * Returns a MongoExtensionByteView containing the view resolution policy of the 
     * associated aggregation stage. 
    */
    MongoExtensionByteView (*get_view_policy)(const MongoExtensionAggStageAstNode* astNode);
};