Make Slack connection error more descriptive (#5007)

# What this PR does

<img width="517" alt="Screenshot 2024-09-10 at 17 11 51"
src="https://github.com/user-attachments/assets/086eb4ae-6ea3-467c-a1ed-6d6f51ddc3e7">


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## Checklist

- [x] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required)
- [x] Added the relevant release notes label (see labels prefixed w/
`release:`). These labels dictate how your PR will
    show up in the autogenerated release notes.

engine/apps/slack/tests/test_interactive_api_endpoint.py

@@ -55,6 +55,38 @@ def slack_team_identity(make_slack_team_identity):
     )
 
 
+@patch("apps.slack.views.SlackEventApiEndpointView.verify_signature", return_value=True)
+@patch("apps.slack.views.SlackEventApiEndpointView._open_warning_window_if_needed")
+@pytest.mark.django_db
+def test_no_user_in_organization_for_slack_team_identity(
+    mock_open_warning_window_if_needed,
+    _mock_verify_signature,
+    make_organization,
+    make_slack_user_identity,
+    slack_team_identity,
+):
+    # only create SlackUserIdentity, not actual OnCall user
+    make_slack_user_identity(slack_team_identity=slack_team_identity, slack_id=SLACK_USER_ID)
+    organization = make_organization(slack_team_identity=slack_team_identity, grafana_url="https://test.com")
+
+    event_payload = {
+        "type": PayloadType.BLOCK_ACTIONS,
+        "trigger_id": EVENT_TRIGGER_ID,
+        "user": {"id": SLACK_USER_ID},
+        "team": {"id": SLACK_TEAM_ID},
+        "actions": [{"value": json.dumps({"organization_id": organization.id})}],
+    }
+
+    response = _make_request(event_payload)
+    assert response.status_code == status.HTTP_200_OK
+
+    mock_open_warning_window_if_needed.assert_called_once_with(
+        event_payload,
+        slack_team_identity,
+        "Permission denied. Please connect your Slack account to OnCall: https://test.com/a/grafana-oncall-app/users/me/",
+    )
+
+
 @patch("apps.slack.views.SlackEventApiEndpointView.verify_signature", return_value=True)
 @patch("apps.slack.views.SlackEventApiEndpointView._open_warning_window_if_needed")
 @pytest.mark.django_db

engine/apps/slack/views.py

@@ -3,6 +3,7 @@
 import json
 import logging
 from contextlib import suppress
+from urllib.parse import urljoin
 
 from django.conf import settings
 from django.core.exceptions import ObjectDoesNotExist
@@ -291,11 +292,13 @@ def post(self, request):
                 return Response()
         elif organization:
             user = slack_user_identity.get_user(organization)
-            if not user:
-                # Means that user slack_user_identity is not in any organization, connected to this Slack workspace
-                warning_text = "Permission denied. Please connect your Slack account to OnCall."
-                # Open pop-up to inform user why OnCall bot doesn't work if any action was triggered
-                self._open_warning_window_if_needed(payload, slack_team_identity, warning_text)
+            if not user:  # SlackUserIdentity exists but not connected to any user in this organization
+                user_settings_url = urljoin(organization.grafana_url, "/a/grafana-oncall-app/users/me/")
+                self._open_warning_window_if_needed(
+                    payload,
+                    slack_team_identity,
+                    f"Permission denied. Please connect your Slack account to OnCall: {user_settings_url}",
+                )
                 return Response(status=200)
         # direct paging / manual incident / schedule update dialogs don't require organization to be set
         elif (