title: How to get the last page of any Firestore query?
body: <p>How do I get the last page of any Firestore query without needing to send the cursor value for the last document in the query? </p>
  
  <p>Obviously the first/last value is not always known unless I manually keep track of those values. I have queries that order by many different fields so having to store first/last cursor values for each of those seems like a lot of unnecessary work. </p>
  
  <p>Getting the entire query result without limit is obviously expensive and impractical.</p>