PD migrator: handle deactivated users in PD when migrating schedules (#1407)

# What this PR does
Handle deactivated users in PD when migrating schedules using PD
migrator.

## Checklist

- [x] Tests updated

tools/pagerduty-migrator/migrator/resources/schedules.py

@@ -132,6 +132,16 @@ class Schedule:
         shifts = []
         errors = []
         for layer in self.layers:
+            # Check if all users in the layer exist in PD
+            deactivated_user_ids = [
+                user_id for user_id in layer.user_ids if user_id not in user_id_map
+            ]
+            if deactivated_user_ids:
+                errors.append(
+                    f"{layer.name}: User IDs {deactivated_user_ids} not found. The users probably have been deactivated in PagerDuty."
+                )
+                continue
+
             # A single PagerDuty layer can result in multiple OnCall shifts
             layer_shifts, error = layer.to_oncall_shifts(user_id_map)
 

tools/pagerduty-migrator/migrator/tests/test_schedules.py

@@ -2,13 +2,11 @@ import datetime
 
 from migrator.resources.schedules import Restriction, Schedule
 
-
-class IdentityMap(dict):
-    def __missing__(self, key):
-        return key
-
-
-user_id_map = IdentityMap()
+user_id_map = {
+    "USER_ID_1": "USER_ID_1",
+    "USER_ID_2": "USER_ID_2",
+    "USER_ID_3": "USER_ID_3",
+}
 
 
 def test_merge_restrictions():
@@ -177,6 +175,34 @@ def test_current_or_next_restriction():
     )
 
 
+def test_deactivated_users():
+    pd_schedule = {
+        "name": "No restrictions",
+        "time_zone": "Europe/London",
+        "schedule_layers": [
+            {
+                "name": "Layer 1",
+                "start": "2023-02-19T19:25:55+00:00",
+                "end": None,
+                "rotation_virtual_start": "2023-02-07T19:00:00+00:00",
+                "rotation_turn_length_seconds": 1209600,
+                "restrictions": [],
+                "users": [
+                    {"user": {"id": "USER_ID_1"}},
+                    {"user": {"id": "USER_ID_DEACTIVATED"}},
+                ],
+            },
+        ],
+    }
+
+    oncall_schedule, errors = Schedule.from_dict(pd_schedule).to_oncall_schedule(
+        user_id_map
+    )
+    assert errors == [
+        "Layer 1: User IDs ['USER_ID_DEACTIVATED'] not found. The users probably have been deactivated in PagerDuty."
+    ]
+
+
 def test_no_restrictions():
     pd_schedule = {
         "name": "No restrictions",