src/vs/platform/userDataSync/common/extensionsStorageSync.ts/ExtensionsStorageSyncService/getKeysForSync
class ExtensionsStorageSyncService:	getKeysForSync(extensionIdWithVersion: IExtensionIdWithVersion): string[] | undefined {
		const extensionKeysForSyncFromProduct = this.productService.extensionSyncedKeys?.[extensionIdWithVersion.id.toLowerCase()];
		const extensionKeysForSyncFromStorageValue = this.storageService.get(ExtensionsStorageSyncService.toKey(extensionIdWithVersion), StorageScope.GLOBAL);
		const extensionKeysForSyncFromStorage = extensionKeysForSyncFromStorageValue ? JSON.parse(extensionKeysForSyncFromStorageValue) : undefined;

		return extensionKeysForSyncFromStorage && extensionKeysForSyncFromProduct
			? distinct([...extensionKeysForSyncFromStorage, ...extensionKeysForSyncFromProduct])
			: (extensionKeysForSyncFromStorage || extensionKeysForSyncFromProduct);
	}