Here's an example I captured from the rabbit bus from a nova example operation showing the problem. The context is *not* part of the o.vo serialization routine in the payload but rather top-level in the message, part of the oslo.messaging marshalling.

{'_context_auth_token': 'gAAAAABk1RkXSSLrJGj3jVFU-9Woyy4cxxSIJt_4JCCjy2ieh0T_HuZE5oOUuVXSvh8WKvvnx9Qe-0AtsRLj5uJDomyqWTifc7bzHjyZHlNTX2GK0sOJSTQcnzrrg5EP_jKFtD51msoH7ZP07rUXHkMBMlJQU5FwRl0bp5qTWP51HJTrgKXxBGc',
 '_context_domain': None,
 '_context_global_request_id': None,
 '_context_is_admin': False,
 '_context_is_admin_project': True,
 '_context_project': 'a45c2f77b50b4ff08a31d26a94346bbb',
 '_context_project_domain': 'default',
 '_context_project_id': 'a45c2f77b50b4ff08a31d26a94346bbb',
 '_context_project_name': 'demo',
 '_context_quota_class': None,
 '_context_read_deleted': 'no',
 '_context_read_only': False,
 '_context_remote_address': '192.168.122.222',
 '_context_request_id': 'req-b1f5ad71-d5ee-4779-8425-888dc52be82b',
 '_context_resource_uuid': None,
 '_context_roles': ['anotherrole', 'member', 'reader'],
 '_context_service_catalog': [{'endpoints': [{'publicURL': 'https://192.168.122.222:9696/networking',
                                              'region': 'RegionOne'}],
                               'name': 'neutron',
                               'type': 'network'},
                              {'endpoints': [{'publicURL': 'https://192.168.122.222/placement',
                                              'region': 'RegionOne'}],
                               'name': 'placement',
                               'type': 'placement'},
                              {'endpoints': [{'publicURL': 'https://192.168.122.222/volume/v3/a45c2f77b50b4ff08a31d26a94346bbb',
                                              'region': 'RegionOne'}],
                               'name': 'cinderv3',
                               'type': 'volumev3'},
                              {'endpoints': [{'publicURL': 'https://192.168.122.222/volume/v3/a45c2f77b50b4ff08a31d26a94346bbb',
                                              'region': 'RegionOne'}],
                               'name': 'cinder',
                               'type': 'block-storage'},
                              {'endpoints': [{'publicURL': 'https://192.168.122.222/image',
                                              'region': 'RegionOne'}],
                               'name': 'glance',
                               'type': 'image'}],
 '_context_show_deleted': False,
 '_context_system_scope': None,
 '_context_timestamp': '2023-08-10T17:06:32.802080',
 '_context_user': '7be5208c3a2c4643a0c2c746acb2716c',
 '_context_user_domain': 'default',
 '_context_user_id': '7be5208c3a2c4643a0c2c746acb2716c',
 '_context_user_identity': '7be5208c3a2c4643a0c2c746acb2716c '
                           'a45c2f77b50b4ff08a31d26a94346bbb - default default',
 '_context_user_name': 'demo',
 '_unique_id': 'c73164b9d6264787a15736264860a91e',
 'event_type': 'instance.create.start',
 'message_id': 'ff466c49-cea1-48d5-9176-ddc7bed75e2f',
 'payload': {'nova_object.data': {'action_initiator_project': 'a45c2f77b50b4ff08a31d26a94346bbb',
                                  'action_initiator_user': '7be5208c3a2c4643a0c2c746acb2716c',
                                  'architecture': None,
                                  'auto_disk_config': 'MANUAL',
                                  'availability_zone': 'nova',
                                  'block_devices': [],
                                  'created_at': '2023-08-10T17:06:35Z',
                                  'deleted_at': None,
                                  'display_description': 'test',
                                  'display_name': 'test',
                                  'fault': None,
                                  'flavor': {'nova_object.data': {'description': None,
                                                                  'disabled': False,
                                                                  'ephemeral_gb': 0,
                                                                  'extra_specs': {'hw_rng:allowed': 'True'},
                                                                  'flavorid': 'd1',
                                                                  'is_public': True,
                                                                  'memory_mb': 512,
                                                                  'name': 'ds512M',
                                                                  'projects': None,
                                                                  'root_gb': 5,
                                                                  'rxtx_factor': 1.0,
                                                                  'swap': 0,
                                                                  'vcpu_weight': 0,
                                                                  'vcpus': 1},
                                             'nova_object.name': 'FlavorPayload',
                                             'nova_object.namespace': 'nova',
                                             'nova_object.version': '1.4'},
                                  'host': None,
                                  'host_name': 'test',
                                  'image_uuid': '1c28437f-a65a-4335-98b2-9d1d5d2075f5',
                                  'instance_name': 'instance-00000079',
                                  'ip_addresses': [],
                                  'kernel_id': '',
                                  'key_name': None,
                                  'keypairs': [],
                                  'launched_at': None,
                                  'locked': False,
                                  'locked_reason': None,
                                  'metadata': {},
                                  'node': None,
                                  'os_type': None,
                                  'power_state': 'pending',
                                  'progress': 0,
                                  'ramdisk_id': '',
                                  'request_id': 'req-b1f5ad71-d5ee-4779-8425-888dc52be82b',
                                  'reservation_id': 'r-wi56jdwr',
                                  'state': 'building',
                                  'tags': [],
                                  'task_state': None,
                                  'tenant_id': 'a45c2f77b50b4ff08a31d26a94346bbb',
                                  'terminated_at': None,
                                  'trusted_image_certificates': None,
                                  'updated_at': None,
                                  'user_id': '7be5208c3a2c4643a0c2c746acb2716c',
                                  'uuid': 'dcd2ee7b-671f-4cae-bffd-d6a6a6945b97'},
             'nova_object.name': 'InstanceCreatePayload',
             'nova_object.namespace': 'nova',
             'nova_object.version': '1.12'},
 'priority': 'INFO',
 'publisher_id': 'nova-compute:jammy',
 'timestamp': '2023-08-10 17:06:36.322476'}