Make emails case-insensitive for ICal schedules (#1297)

# What this PR does
Fixes a bug when current on-call users for web UI and Slack user group
are incorrect.

This happens when both conditions below are true:
- Using an ICal schedule
- Email of a user in Grafana has a different case than an event in ICal
(e.g. `User@gmail.com` in Grafana, `user@gmail.com` in ICal event)

The bug was introduced by https://github.com/grafana/oncall/pull/1169

## Which issue(s) this PR fixes
https://github.com/grafana/oncall/issues/1296

## Checklist

- [x] Tests updated
- [x] `CHANGELOG.md` updated

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Fixed
+
+- Fix bug with email case sensitivity for ICal on-call schedules ([1297](https://github.com/grafana/oncall/pull/1297))
+
 ## v1.1.22 (2023-02-03)
 
 ### Fixed

engine/apps/schedules/ical_utils.py

@@ -72,7 +72,11 @@ def users_in_ical(
 
     if users_to_filter is not None:
         return list(
-            {user for user in users_to_filter if user.username in usernames_from_ical or user.email in emails_from_ical}
+            {
+                user
+                for user in users_to_filter
+                if user.username in usernames_from_ical or user.email.lower() in emails_from_ical
+            }
         )
 
     users_found_in_ical = organization.users

engine/apps/schedules/tests/calendars/override_email_case_sensitivity.ics

@@ -0,0 +1,21 @@
+BEGIN:VCALENDAR
+PRODID:-//Google Inc//Google Calendar 70.9054//EN
+VERSION:2.0
+CALSCALE:GREGORIAN
+METHOD:PUBLISH
+X-WR-CALNAME:test
+X-WR-TIMEZONE:Europe/London
+BEGIN:VEVENT
+DTSTART:20230206T110000Z
+DTEND:20230206T120000Z
+DTSTAMP:20230206T112228Z
+UID:16m6o1qji0fdg49coeflc202ss@google.com
+CREATED:20230206T112217Z
+DESCRIPTION:
+LAST-MODIFIED:20230206T112217Z
+SEQUENCE:0
+STATUS:CONFIRMED
+SUMMARY:Test@TEST.test
+TRANSP:OPAQUE
+END:VEVENT
+END:VCALENDAR

engine/apps/schedules/tests/test_custom_on_call_shift.py

@@ -1382,6 +1382,37 @@ def test_get_oncall_users_for_multiple_schedules(
     )
 
 
+@pytest.mark.django_db
+def test_get_oncall_users_for_multiple_schedules_emails_case_insensitive(
+    get_ical,
+    make_organization,
+    make_user_for_organization,
+    make_on_call_shift,
+    make_schedule,
+):
+    """
+    Test that emails are case insensitive when matching users to on-call shifts.
+    https://github.com/grafana/oncall/issues/1296
+    """
+    organization = make_organization()
+
+    # user's email case is the opposite of the one in the ICal file below (Test@TEST.test)
+    user = make_user_for_organization(organization, email="tEST@test.TEST")
+    schedule = make_schedule(organization, schedule_class=OnCallScheduleCalendar)
+
+    # Load ICal file with an event for user with email Test@TEST.test for 6 February 2023, 11:00 UTC - 12:00 UTC
+    calendar = get_ical("override_email_case_sensitivity.ics")
+    schedule.cached_ical_file_overrides = calendar.to_ical().decode()
+    schedule.save(update_fields=["cached_ical_file_overrides"])
+
+    # Get on-call users for 6 February 2023 11:30 UTC
+    events_datetime = timezone.datetime(2023, 2, 6, 11, 30, tzinfo=timezone.utc)
+    schedules = OnCallSchedule.objects.filter(pk=schedule.pk)
+    oncall_users = schedules.get_oncall_users(events_datetime=events_datetime)
+
+    assert oncall_users == {schedule.pk: [user]}
+
+
 @pytest.mark.django_db
 def test_shift_convert_to_ical(make_organization_and_user, make_on_call_shift):
     organization, user = make_organization_and_user()