It seems that  delta_percent values are null for all daily items in daily OCI storage delta report.

Note that delta percent values in metadata, as well as in storage report with monthly resolution or any type of instance-type/cost reports are all ok.

Steps to reproduce:

1. ingest oci source - for example place breakpoint() to test_api_oci_ingest_single_source test, run it and wait till the ingestion is finished
2. request OCI storage delta report for current month with daily resolution:
   [http://localhost:8000/api/cost-management/v1/reports/oci/storage/?filter[resolution]=daily&filter[time_scope_value]=-1&filter[time_scope_units]=month&delta=usage]

Check delta_percent values in the items for each day -  you will see  "delta_percent": null (unexpected)

        {
            "date": "2023-01-01",
            "values": [
                {
                    "date": "2023-01-01",
                    "sup_credit": 0.0,
                    "usage": {
                        "value": 0.000556872,
                        "units": "GB-Mo"
                    },
                    "source_uuid": [
                        "c0c1b9f3-6526-4d9d-b7f5-082d1df11f24"
                    ],
                    "delta_value": -0.000269496,
                    "delta_percent": null,
                    "infrastructure": {...}
                    },
                    "supplementary": {...}
                    },
                    "cost": {...}
                    }
                }
            ]
        }, 

This bug is not visible in UI -> setting priority to Minor