Google Calendar Integration + automatic Shift Swap Request generation (#4220)

# What this PR does

## Which issue(s) this PR closes

Closes https://github.com/grafana/oncall-private/issues/2591

## Checklist

- [ ] Unit, integration, and e2e (if applicable) tests updated (N/A)
- [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.

docs/sources/manage/on-call-schedules/shift-swaps/index.md

@@ -98,6 +98,24 @@ You can also check (and take) a swap request details in the web UI.
 
 Once a swap is taken, the affected rotations and the final schedule will reflect the changes.
 
+## Google Calendar Integration
+
+Grafana OnCall allows you to connect your Google user to your OnCall user, giving us read-only access to your
+Google Calendar's Out of Office events. We periodically check your Out of Office events to see if these overlap
+with any of your on-call shifts. If so, we'll go ahead and automatically generate a shift swap request for you!
+
+To link your Google user, simply head over to "View my profile" on the OnCall "Users" page. From there, follow the steps
+under the Google Calendar tab. Once linked, you can further configure things, such as which OnCall schedules you would
+like us to consider for automatic shift swap generation (by default we will consider all of the schedules that you
+are involved in).
+
+### Configuring for open source
+
+1. Follow the instructions [here](https://developers.google.com/identity/protocols/oauth2) to setup your Google OAuth2
+application.
+2. Create a Client ID for your OAuth2 app and set the `SOCIAL_AUTH_GOOGLE_OAUTH2_KEY` and `SOCIAL_AUTH_GOOGLE_OAUTH2_SECRET`
+environment variables accordingly.
+
 {{% docs/reference %}}
 [mobile push notification]: "/docs/oncall/ -> /docs/oncall/<ONCALL_VERSION>/manage/mobile-app/push-notifications#shift-swap-notifications"
 [mobile push notification]: "/docs/grafana-cloud/ -> /docs/grafana-cloud/alerting-and-irm/oncall/manage/mobile-app/push-notifications#shift-swap-notifications"

engine/apps/api/views/features.py

@@ -65,7 +65,7 @@ class FeaturesAPIView(APIView):
         if is_labels_feature_enabled(self.request.auth.organization):
             enabled_features.append(Feature.LABELS)
 
-        if settings.FEATURE_GOOGLE_OAUTH2_ENABLED:
+        if settings.GOOGLE_OAUTH2_ENABLED:
             enabled_features.append(Feature.GOOGLE_OAUTH2)
 
         return enabled_features

engine/settings/base.py

@@ -71,7 +71,6 @@ GRAFANA_CLOUD_NOTIFICATIONS_ENABLED = getenv_boolean("GRAFANA_CLOUD_NOTIFICATION
 FEATURE_LABELS_ENABLED_FOR_ALL = getenv_boolean("FEATURE_LABELS_ENABLED_FOR_ALL", default=False)
 # Enable labels feature for organizations from the list. Use OnCall organization ID, for this flag
 FEATURE_LABELS_ENABLED_PER_ORG = getenv_list("FEATURE_LABELS_ENABLED_PER_ORG", default=list())
-FEATURE_GOOGLE_OAUTH2_ENABLED = getenv_boolean("FEATURE_GOOGLE_OAUTH2_ENABLED", default=False)
 
 TWILIO_API_KEY_SID = os.environ.get("TWILIO_API_KEY_SID")
 TWILIO_API_KEY_SECRET = os.environ.get("TWILIO_API_KEY_SECRET")
@@ -650,15 +649,17 @@ AUTHENTICATION_BACKENDS = [
     "apps.social_auth.backends.GoogleOAuth2",
 ]
 
-if FEATURE_GOOGLE_OAUTH2_ENABLED:
+SOCIAL_AUTH_GOOGLE_OAUTH2_KEY = os.environ.get("SOCIAL_AUTH_GOOGLE_OAUTH2_KEY")
+SOCIAL_AUTH_GOOGLE_OAUTH2_SECRET = os.environ.get("SOCIAL_AUTH_GOOGLE_OAUTH2_SECRET")
+GOOGLE_OAUTH2_ENABLED = SOCIAL_AUTH_GOOGLE_OAUTH2_KEY is not None and SOCIAL_AUTH_GOOGLE_OAUTH2_SECRET is not None
+
+if GOOGLE_OAUTH2_ENABLED:
     CELERY_BEAT_SCHEDULE["sync_google_calendar_out_of_office_events_for_all_users"] = {
         "task": "apps.google.tasks.sync_out_of_office_calendar_events_for_all_users",
         "schedule": crontab(minute="*/30"),  # every 30 minutes
         "args": (),
     }
 
-SOCIAL_AUTH_GOOGLE_OAUTH2_KEY = os.environ.get("SOCIAL_AUTH_GOOGLE_OAUTH2_KEY")
-SOCIAL_AUTH_GOOGLE_OAUTH2_SECRET = os.environ.get("SOCIAL_AUTH_GOOGLE_OAUTH2_SECRET")
 # NOTE: for right now we probably only need the calendar.events.readonly scope
 # however, if we want to write events back to the user's calendar
 # we'll probably need to change this to the calendar.events scope