test: cover PATCH /dids/:id unassigning emergency_calling_service

Add wire-level test for unassigning an EmergencyCallingService from a
Did by sending emergency_calling_service: {data: null} in the PATCH
request body. Includes a fixture with the expected 200 response showing
emergency_calling_service data: null in relationships.

Author: Fivell

tests/fixtures/dids/update_unassign_ecs.yaml

@@ -0,0 +1,22 @@
+interactions:
+- request:
+    body: '{"data":{"id":"44957076-778a-4802-b60c-d22db0cda284","type":"dids","attributes":{},"relationships":{"emergency_calling_service":{"data":null}}}}'
+    headers:
+      Accept:
+      - application/vnd.api+json
+      Api-Key:
+      - test-api-key
+      Content-Type:
+      - application/vnd.api+json
+    method: PATCH
+    uri: https://sandbox-api.didww.com/v3/dids/44957076-778a-4802-b60c-d22db0cda284
+  response:
+    body:
+      string: '{"data":{"id":"44957076-778a-4802-b60c-d22db0cda284","type":"dids","attributes":{"blocked":false,"capacity_limit":1,"description":"string","terminated":false,"awaiting_registration":false,"number":"437xxxxxxxxx","expires_at":"2026-06-25T08:21:41.795Z","channels_included_count":2,"created_at":"2026-06-25T08:21:41.795Z","billing_cycles_count":1,"dedicated_channels_count":0,"emergency_enabled":false},"relationships":{"did_group":{"links":{"self":"https://sandbox-api.didww.com/v3/dids/44957076-778a-4802-b60c-d22db0cda284/relationships/did_group","related":"https://sandbox-api.didww.com/v3/dids/44957076-778a-4802-b60c-d22db0cda284/did_group"}},"emergency_calling_service":{"links":{"self":"https://sandbox-api.didww.com/v3/dids/44957076-778a-4802-b60c-d22db0cda284/relationships/emergency_calling_service","related":"https://sandbox-api.didww.com/v3/dids/44957076-778a-4802-b60c-d22db0cda284/emergency_calling_service"},"data":null}}},"meta":{"api_version":"2026-04-16"}}'
+    headers:
+      Content-Type:
+      - application/vnd.api+json
+    status:
+      code: 200
+      message: OK
+version: 1

tests/resources/test_did.py

@@ -178,3 +178,26 @@ def test_update_did_invalid_trunk_group_error(self, client):
         assert exc_info.value.status_code == 422
         assert len(exc_info.value.errors) == 1
         assert "voice_in_trunk_group" in exc_info.value.errors[0]["detail"]
+
+    def test_unassign_emergency_calling_service_request_body(self):
+        """Nulling emergency_calling_service must send relationship data: null."""
+        did = Did.build("44957076-778a-4802-b60c-d22db0cda284")
+        did._null_relationship("emergency_calling_service")
+        doc = did.to_jsonapi(include_id=True, dirty_only=True)
+        assert doc == {
+            "id": "44957076-778a-4802-b60c-d22db0cda284",
+            "type": "dids",
+            "attributes": {},
+            "relationships": {
+                "emergency_calling_service": {"data": None},
+            },
+        }
+
+    @my_vcr.use_cassette("dids/update_unassign_ecs.yaml")
+    def test_update_did_unassign_emergency_calling_service(self, client):
+        did = Did.build("44957076-778a-4802-b60c-d22db0cda284")
+        did._null_relationship("emergency_calling_service")
+        response = client.dids().update(did)
+        updated = response.data
+        assert updated.id == "44957076-778a-4802-b60c-d22db0cda284"
+        assert updated.emergency_enabled is False