slack webhooks: Eliminate unnecessary use of Service model.

The user ID of the bot user is a much more useful value to be sending
to the third-party API here.

zerver/lib/outgoing_webhook.py

@@ -85,7 +85,6 @@ class SlackOutgoingWebhookService(OutgoingWebhookServiceInterface):
         if event['message']['type'] == 'private':
             raise NotImplementedError("Private messaging service not supported.")
 
-        service = get_service_profile(event['user_profile_id'], str(self.service_name))
         request_data = [("token", self.token),
                         ("team_id", event['message']['sender_realm_str']),
                         ("team_domain", email_to_domain(event['message']['sender_email'])),
@@ -96,7 +95,7 @@ class SlackOutgoingWebhookService(OutgoingWebhookServiceInterface):
                         ("user_name", event['message']['sender_full_name']),
                         ("text", event['command']),
                         ("trigger_word", event['trigger']),
-                        ("service_id", service.id),
+                        ("service_id", event['user_profile_id']),
                         ]
 
         return rest_operation, request_data

zerver/tests/test_outgoing_webhook_interfaces.py

@@ -76,8 +76,7 @@ class TestSlackOutgoingWebhookService(ZulipTestCase):
                                                    user_profile=None,
                                                    service_name='test-service')
 
-    @mock.patch('zerver.lib.outgoing_webhook.get_service_profile', return_value=mock_service)
-    def test_process_event(self, mock_get_service_profile: mock.Mock) -> None:
+    def test_process_event(self) -> None:
         rest_operation, request_data = self.handler.process_event(self.event)
 
         self.assertEqual(rest_operation['base_url'], 'http://example.domain.com')
@@ -92,7 +91,7 @@ class TestSlackOutgoingWebhookService(ZulipTestCase):
         self.assertEqual(request_data[7][1], "Sample User")  # user_name
         self.assertEqual(request_data[8][1], "@**test**")  # text
         self.assertEqual(request_data[9][1], "mention")  # trigger_word
-        self.assertEqual(request_data[10][1], mock_service.id)  # service_id
+        self.assertEqual(request_data[10][1], 12)  # user_profile_id
 
     def test_process_success(self) -> None:
         response = mock.Mock(spec=Response)