Referencing Storage account access keys in Bicep

listStorageAccountKeys.bicep

resource existingStorageAccount 'Microsoft.Storage/storageAccounts@2023-05-01' existing = {
  name: storageAccountName
}

resource existingWebApp 'Microsoft.Web/sites@2020-09-01' existing = {
  name: webAppName
}

resource siteConfig 'Microsoft.Web/sites/config@2023-12-01' = {
  parent: existingWebApp
  name: 'web'
  properties: {
    // ... redacted
    azureStorageAccounts: {
      ContentFilesVolume: {
        type: 'AzureFiles'
        accountName: existingStorageAccount.name
        shareName: fileShareName
        mountPath: containerMountPath
        accessKey: existingStorageAccount.listKeys().keys[0].value
      }
    }
  }
}