On the backend server, it should inject the configuration of the feature flag to the frontend web page.

This means that the "index.html" page can not be served as a static file anymore. We may need to read it in to memory, inject the configuration, and then return to the clients on request.

See https://github.com/facebook/create-react-app/blob/master/packages/react-scripts/template/README.md#injecting-data-from-the-server-into-the-page for more details.
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