(DOCS-16318): serverStatus expireAfterSeconds metric for change streams (#4850)

* (DOCS-16318): serverStatus expireAfterSeconds metric for change streams

* review edits

* add new metric to release notes

* alphabetize

* copy review feedback

Author: jeff-allen-mongo

source/reference/command/serverStatus.txt

@@ -280,8 +280,9 @@ changeStreamPreImages
          scannedCollections : <num>,
          scannedInternalCollections : <num>,
          maxStartWallTimeMillis : <num>,
-         timeElapsedMillis : <num>
-      }
+         timeElapsedMillis : <num>,
+      },
+      expireAfterSeconds : <num>
    }
 
 A document that reports metrics related to 
@@ -336,6 +337,15 @@ A document that reports metrics related to
         - Cumulative time in milliseconds of all deletion passes by the 
           purging job.
 
+.. serverstatus:: changeStreamPreImages.expireAfterSeconds
+
+   .. versionadded:: 7.1
+
+   Amount of time in seconds that MongoDB retains pre-images. If
+   :parameter:`~changeStreamOptions.preAndPostImages.expireAfterSeconds`
+   is not defined, this metric does not appear in the ``serverStatus``
+   output.
+
 .. _server-status-connections:
 
 connections

source/release-notes/7.1.txt

@@ -113,10 +113,12 @@ serverStatus Output Change
 output:
 
 Change Stream Metrics 
-  :serverstatus:`metrics.changeStreams.showExpandedEvents`
+  - :serverstatus:`changeStreamPreImages.expireAfterSeconds`
+  
+  - :serverstatus:`metrics.changeStreams.showExpandedEvents`
 
 Query Stats Metrics
-  :serverstatus:`queryStats`
+  - :serverstatus:`queryStats`
 
 .. toctree::
    :titlesonly: