title: Convert Future to Mono
body: <p>I have legacy code which returns convert java.util.concurrent.Future, now I am supposed to wrap this method call in a layer which returns reactor publishers Mono or Flux. I believe approach to convert to either of them should be similar so what is the correct way to convert it to Mono.</p>
  
  <p>Suppose for example I am getting Future from API and I need Mono </p>