Update chargeperiod.md

Adding OCI mappings in supporting content for chargeperiod.

supporting_content/dimensions/chargeperiod.md

@@ -9,6 +9,7 @@ Current column mappings found in available data sets:
 | AWS       | CUR                     | line_item_usage_start_date<br>line_item_usage_end_date|
 | GCP       | BigQuery Billing Export | From the BigQuery billing export, every line item has two dates:<br><br>- usage_start_time - TIMESTAMP<br>    2018-07-02 03:00:00 UTC<br>- usage_end_time - TIMESTAMP<br>    2018-07-02 04:00:00 UTC<br><br>The start time is inclusive and the end time is exclusive.   The moment defined by usage_end_time is then used to define a usage_start_time for subsequent cost line items.<br>In addition to these two fields, there is usage data that could have an impact on usage duration and measuring a usage period:<br>- usage.amount<br>- usage.unit<br>- usage.amount_in_pricing_units<br>- usage.pricing_unit |
 | Microsoft | Cost details            | Azure cost export contains a “date” field with the assumption that the cost details.  <br><br>This date field is a Timestamp with 00:00:00 UTC time.<br>2018-07-03 00:00:00UTC|
+| OCI | Cost reports | lineItem/intervalUsageStart<br>lineItem/intervalUsageEnd |
 
 ## Example usage scenarios