add section about logging

Signed-off-by: aramissennyeydd <aramis.sennyey@doordash.com>

docs/plugins/observability.md

@@ -15,6 +15,32 @@ See how to install Datadog Events in your app
 
 ## Logging
 
+### New Backend
+
+The backend supplies a central logging service, [`rootLogger`](../backend-system/core-services/root-logger.md), as well as a plugin based logger, [`logger`](../backend-system/core-services/logger.md) from `coreServices`. To add additional granularity to your logs, you can create children from the plugin based logger, using the `.child()` method and provide is with JSON data. For example, if you wanted to log items for a specific span in your plugin, you could do
+
+```ts
+export function createRouter({ logger }) {
+  const router = Router();
+
+  router.post('/task/:taskId/queue', (req, res) => {
+    const { taskId } = req.params;
+    const taskLogger = logger.child({ task: taskId });
+    taskLogger.log('Queueing this task.');
+  });
+
+  router.get('/task/:taskId/results', (req, res) => {
+    const { taskId } = req.params;
+    const taskLogger = logger.child({ task: taskId });
+    taskLogger.log('Getting the results of this task.');
+  });
+}
+```
+
+You can also add additional metadata to all logs for your Backstage instance by overriding the `rootLogger` implementation, you can see an example in [the `logger` docs](../backend-system/core-services/logger.md#configuring-the-service).
+
+### Old Backend
+
 The backend supplies a central [winston](https://github.com/winstonjs/winston)
 root logger that plugins are expected to use for their logging needs. In the
 default production setup, it emits structured JSON logs on stdout, with a field