now.json

{
  "env": {
    "NEXT_EXAMPLE_CMS_CONTENTFUL_SPACE_ID": "@next_example_contentful_space_id",
    "NEXT_EXAMPLE_CMS_CONTENTFUL_ACCESS_TOKEN": "@next_example_cms_contentful_access_token",
    "NEXT_EXAMPLE_CMS_CONTENTFUL_PREVIEW_ACCESS_TOKEN": "@next_example_cms_contentful_preview_access_token",
    "NEXT_EXAMPLE_CMS_CONTENTFUL_PREVIEW_SECRET": "@next_example_cms_contentful_preview_secret"
  },
  "build": {
    "env": {
      "NEXT_EXAMPLE_CMS_CONTENTFUL_SPACE_ID": "@next_example_contentful_space_id",
      "NEXT_EXAMPLE_CMS_CONTENTFUL_ACCESS_TOKEN": "@next_example_cms_contentful_access_token",
      "NEXT_EXAMPLE_CMS_CONTENTFUL_PREVIEW_ACCESS_TOKEN": "@next_example_cms_contentful_preview_access_token"
    }
  }
}