Webhook sends multiple requests when updating tags

[nahun]

NetBox version

v2.11.1

Python version

3.8

Steps to Reproduce

1. Create webhook for DCIM->Interface (or any model I found so far)
2. Check all event types
3. URL: http://localhost:9000/
4. HTTP method: POST
5. HTTP content type: application/json
6. Uncheck SSL verification
7. Start the webhook receiver: python netbox/manage.py webhook_receiver
8. Add or remove tags from an existing interface or create a new interface with tags defined

Expected Behavior

One HTTP request sent to the webhook receiver.

Observed Behavior

The webhook receiver will show multiple HTTP requests for a single interface being updated.

[jeremystretch]

This happens due the way objects are saved in the database. When you create or update an object with tags assigned, two things happen:

1. The row is created/saved in its table and the post_save signal is fired, triggering a webhook.
2. Tag assignments to the object are created in the database and the m2m_changed signal is fired, triggering a second webhook.

You'll notice that the first webhook doesn't specify any tags assigned to the object, whereas the second one does.

We can probably devise a way to avoid firing two webhooks, however it will likely require delaying the queuing of webhooks until the request has been processed.