DOCSP-35753 serverStatus metric stepDown moved to stateTransaction (#5927) (#6036)

* DOCSP-35753-serverStatus-metric-stepDown-moved-to-stateTransaction

* DOCSP-35753: Adding stateTransition object for replication stepDown info. Deprecating stepDown metric and linking to new object.

* Empty-Commit

* DOCSP-35753: Removing references to unsupported previous behavior. Added missing heading for lasteStateTransaction. Modified language per style guide.

* DOCSP-35753: Fixing monospace issue.

* DOCSP-35753: Typo fix

* DOCSP-35753: Small editorial changes per feedback.

Author: mmaville-mdb

source/reference/command/serverStatus.txt

@@ -1799,7 +1799,8 @@ metrics
          reconfig : {
             numAutoReconfigsForRemovalOfNewlyAddedFields : Long("<num>")
          },
-         stepDown : {
+         stateTransition : {
+            lastStateTransition : <string>,
             userOperationsKilled : Long("<num>"),
             userOperationsRunning : Long("<num>")
          },
@@ -2572,26 +2573,52 @@ metrics
 
    .. versionadded:: 5.0
 
-.. serverstatus:: metrics.repl.stepDown
+.. serverstatus:: metrics.repl.stateTransition
 
-   Information on user operations that were running when the
-   :binary:`~bin.mongod` stepped down.
+   Information on user operations when the member undergoes one of the
+   following transitions that can stop user operations:
 
-   .. versionadded:: 4.2
+   - The member steps up to become a primary.
 
-.. serverstatus:: metrics.repl.stepDown.userOperationsKilled
+   - The member steps down to become a secondary.
 
-   The number of user operations killed when the :binary:`~bin.mongod`
-   stepped down.
+   - The member is actively performing a rollback.
 
-   .. versionadded:: 4.2
+.. serverstatus:: metrics.repl.stateTransition.lastStateTransition
 
-.. serverstatus:: metrics.repl.stepDown.userOperationsRunning
+   The transition being reported:
 
-   The number of user operations that remained running when the
-   :binary:`~bin.mongod` stepped down.
+   .. list-table::
+      :widths: 20 80
+      :header-rows: 1
 
-   .. versionadded:: 4.2
+      * - State Change
+        - Description
+
+      * - ``"stepUp"``
+
+        - The member steps up to become a primary.
+
+      * - ``"stepDown"``
+        - The member steps down to become a secondary.
+
+      * - ``"rollback"``
+
+        - The member is actively performing a rollback.
+
+      * - ``""``
+
+        - The member has not undergone any state changes.
+
+.. serverstatus:: metrics.repl.stateTransition.userOperationsKilled
+
+   The number of user operations stopped during the
+   :binary:`~bin.mongod` instance's state change.
+
+.. serverstatus:: metrics.repl.stateTransition.userOperationsRunning
+
+   The number of user operations that remained running during the
+   ``mongod`` instance's state change.
 
 .. serverstatus:: metrics.repl.syncSource