docs: re-add studio document validation and change code snippet

pages/docs/tutorials/studio-document-validation.md

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+---
+title: "Validate AsyncAPI document with Studio"
+description: This tutorial will teach you how to validate AsyncAPI documents using the AsyncAPI Studio tool.
+weight: 120
+---
+
+## Introduction
+This tutorial will teach you how to validate AsyncAPI documents using the [AsyncAPI Studio tool](https://studio.asyncapi.com/).
+
+You will start with a broken AsyncAPI document and troubleshoot via console errors step-by-step until we end up with a valid AsyncAPI document. This process will illustrate how to identify [`REQUIRED` properties in AsyncAPI documents](https://www.asyncapi.com/docs/reference/specification/latest#A2SObject).
+
+## Background context
+An AsyncAPI document is a file that defines and annotates the different components of a specific Event-Driven API. The format of the file must be JSON or YAML. You can use this document to generate both documentation and code.
+
+The AsyncAPI Studio tool allows you to develop an AsyncAPI document, validate it, preview it, convert it to the latest version, and visualize event flows.
+
+Now let's experiment with an invalid file to see how errors are displayed and how to make that file valid again.
+
+## Copy invalid AsyncAPI document
+Let's pretend we have an invalid AsyncAPI document.
+
+1. Open [Studio](https://studio.asyncapi.com/).
+
+<Remember>
+
+You can also skip the step below by clicking on New File in Studio and opening the Invalid Example template in the tutorials section.
+
+</Remember>
+
+2. Copy and paste the below invalid AsyncAPI document:
+
+```yaml
+asyncapi: 3.0.0
+info:
+  title: Streetlights API
+  version: '1.0.0'
+  description: |
+    The Smartylighting Streetlights API allows you
+    to remotely manage the city lights.
+  license:
+    name: Apache 2.0
+    url: 'https://www.apache.org/licenses/LICENSE-2.0'
+
+servers:
+  mosquitto:
+    url: test.mosquitto.org
+    protocol: mqtt
+
+channels:
+  lightMeasured:
+    address: 'light/measured'
+    messages:
+      lightMeasuredMessage:
+        name: LightMeasured
+        payload:
+          type: object
+          properties:
+            id:
+              type: integer
+              minimum: true
+              description: Id of the streetlight.
+            lumens:
+              type: integer
+              minimum: 0
+              description: Light intensity measured in lumens.
+            sentAt:
+              type: string
+              format: date-time
+              description: Date and time when the message was sent.
+
+operations:
+  onLightMeasured:
+    action: 'receive'
+    summary: Inform about environmental lighting conditions for a particular streetlight.
+    channel:
+      $ref: '#/channels/lightMeasured'
+``` 
+
+## Troubleshoot Studio errors
+Let's fix the errors one by one until we end up with a valid AsyncAPI document.
+
+1. You can see the error message on the screen: `Empty or invalid document. Please fix errors/define AsyncAPI document.`
+
+2. Open **DIAGNOSTICS**, you can see more information related to your errors.
+
+3. Fix the incorrect server information. Use `host` instead of `url`
+
+```yaml
+servers:
+  mosquitto:
+    host: test.mosquitto.org
+    protocol: mqtt
+```
+<Remember>
+Notice how <b>description</b> property is missing; that doesn't make the AsyncAPI document invalid, but it's always better to include.
+</Remember>
+
+4. Read the next error: `"minimum" property type must be number`. Fix the `minimum` by changing it to: `0`.
+
+```yaml
+          properties:
+            id:
+              type: integer
+              minimum: 0
+``` 
+5. Congratulations! You identified and fixed all the errors, and now have a valid AsyncAPI document.
+
+## Summary
+This tutorial taught us how to validate an AsyncAPI document using the AsyncAPI Studio tool. We also learned to troubleshoot an invalid AsyncAPI document by following the error message directions in diagnostics. In doing so, we learned how to identify `REQUIRED` properties in all AsyncAPI documents.
+
+## Next steps
+Now that you have completed this tutorial, go ahead to learn [generate AsyncAPI messages (events)](/docs/tutorials/generate-code) which you will be sending to your application.
+
+You may also enjoy reading our [AsyncAPI document validation guide](/docs/guides/validate).
+
+---