Function manifest_json 

pub fn manifest_json(
    app: &App,
    functions: &FunctionRegistry,
    api_base_url: String,
    email_enabled: bool,
) -> Result<String>

The manifest for an app already loaded by the server, as JSON.

api_base_url is the prefix the dashboard puts in front of every request; served from the app’s own origin that is just the API’s base_path.