add wiki to allow overriding default COO

docs/tutorial/AllowDataIngestionFromCertainCOO.md

+We can allow certain country as a valid COO(Country of Origin) by uploading customized legal configuration file into cloud storage. It will override the default configuration for legal service.
+
+Following steps can be taken to allow a specific COO:
+
+1. Refer to following example and create a `Legal_COO.json` file:
+```
+[{
+  "name": "Brazil",
+  "alpha2": "BR",
+  "numeric": 76,
+  "residencyRisk": "Client consent required",
+  "typesNotApplyDataResidency": ["Transferred Data"]
+}]
+```
+
+To obtain the proper alpha, numeric code, and data types without applying data residency constraints (`alpha2`, `numeric`, `typesNotApplyDataResidency` fields), please refer to the [Legal Service Default Configuration](https://community.opengroup.org/osdu/platform/security-and-compliance/legal/-/blob/master/legal-core/src/main/resources/DefaultCountryCode.json).
+then enter the appropriate restriction level in the `residencyRisk` field.
+
+__NOTE:__ Usually we set `residencyRisk` to `Client consent required` when we are allowing data from this country as an exception, but please consult with business if this is the correct value here.
+
+2. Go to cloud storage location where we store legal config file, taking `Azure resource group - dev dp1` as an example:  
+
+   <br/>![](images/PartitionDataContainer.png)
+
+4. Go to the `legal-service-azure-configuration` container and upload the `Legal_COO.json` file created in step 1, replace the existing item with the same name if existed:
+
+   <br/>![](images/UploadFile.png)
+
+   __NOTE:__ Please make sure the file name is exactly the same with the existing file (`Legal_COO.json`), it's case-sensitive.
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