Implements #81 - webhook event backend (#1640)

* merge branch develop

* bugfix, signals for virtualization's class wasn't correctly defined

* updated webhooks for 2.4 and cleanup

* updated docs to cover changes to supervisor config

* review changes and further cleanup

* updated redis connection settings

* cleanup settings

netbox/extras/webhooks_worker.py

@@ -0,0 +1,52 @@
+import requests
+import hmac
+import hashlib
+from rq.utils import import_attribute
+
+from django_rq import job
+
+from extras.constants import WEBHOOK_CT_JSON, WEBHOOK_CT_X_WWW_FORM_ENCODED
+
+
+@job('default')
+def process_webhook(webhook, data, model_class, event, timestamp):
+    """
+    Make a POST request to the defined Webhook
+    """
+    payload = {
+        'event': event,
+        'timestamp': timestamp,
+        'model': model_class.__name__,
+        'data': data
+    }
+    headers = {
+        'Content-Type': webhook.get_http_content_type_display(),
+    }
+    params = {
+        'method': 'POST',
+        'url': webhook.payload_url,
+        'headers': headers
+    }
+
+    if webhook.http_content_type == WEBHOOK_CT_JSON:
+        params.update({'json': payload})
+    elif webhook.http_content_type == WEBHOOK_CT_X_WWW_FORM_ENCODED:
+        params.update({'data': payload})
+
+    prepared_request = requests.Request(**params).prepare()
+
+    if webhook.secret != '':
+        # sign the request with the secret
+        hmac_prep = hmac.new(bytearray(webhook.secret, 'utf8'), prepared_request.body, digestmod=hashlib.sha512)
+        prepared_request.headers['X-Hook-Signature'] = hmac_prep.hexdigest()
+
+    with requests.Session() as session:
+        session.verify = webhook.ssl_verification
+        response = session.send(prepared_request)
+
+    if response.status_code >= 200 and response.status_code <= 299:
+        return 'Status {} returned, webhook successfully processed.'.format(response.status_code)
+    else:
+        raise requests.exceptions.RequestException(
+            "Status {} returned, webhook FAILED to process.".format(response.status_code)
+        )