Add log() in stream-error.md (#24522)

* Add log() in stream-error.md (#23722)

akka-docs/src/test/scala/docs/stream/cookbook/RecipeLoggingElements.scala

@@ -30,7 +30,13 @@ class RecipeLoggingElements extends RecipeSpec {
       //#log-custom
       // customise log levels
       mySource.log("before-map")
-        .withAttributes(Attributes.logLevels(onElement = Logging.WarningLevel))
+        .withAttributes(
+          Attributes.logLevels(
+            onElement = Logging.WarningLevel,
+            onFinish = Logging.InfoLevel,
+            onFailure = Logging.DebugLevel
+          )
+        )
         .map(analyse)
 
       // or provide custom logging adapter
@@ -42,9 +48,16 @@ class RecipeLoggingElements extends RecipeSpec {
       EventFilter.debug(start = "[custom] Element: ").intercept {
         loggedSource.runWith(Sink.ignore)
       }
-
     }
 
+    "use log() for error logging" in {
+      //#log-error
+      Source(-5 to 5)
+        .map(1 / _) //throwing ArithmeticException: / by zero
+        .log("error logging")
+        .runWith(Sink.ignore)
+      //#log-error
+    }
   }
 
 }