docs (oracle-oci): add description and example for create_vnic_details

website/pages/docs/builders/oracle/oci.mdx

@@ -140,6 +140,13 @@ builder.
 - `instance_defined_tags` (map of maps of strings) - Add one or more defined tags for a given namespace
   to the instance used for the image creation process.
 
+- `create_vnic_details` (map of strings) - Specify details for the virtual network interface card (VNIC)
+  that get attached to the instance. Possible keys (all optional) are: `assign_public_ip` (bool),
+  `display_name` (string), `hostname_lable` (string), `nsg_ids` (list), `private_ip` (string),
+  `skip_source_dest_check` (bool), and `subnet_id` (string). See
+  [the Oracle docs](https://docs.cloud.oracle.com/en-us/iaas/Content/Network/Tasks/managingVNICs.htm)
+  for more information about VNICs.
+
 - `use_private_ip` (boolean) - Use private ip addresses to connect to the
   instance via ssh.
 
@@ -244,3 +251,43 @@ Build 'oracle-oci' finished.
 --> oracle-oci: An image was created: 'ExampleImage' (OCID: ocid1.image.oc1.phx.aaa) in region 'us-phoenix-1'
 [opc@packerhost ~]$
 ```
+
+## Auto-assign Tags and Network Security Groups to Instance
+Tags are useful for breaking down costs and usage. The keys `instance_tags`
+and `instance_defined_tags` are assigned to the temporary instance,
+whereas `tags` and `defined_tags` are assigned to the resulting image.
+
+Network Security Groups (NSGs) are used for granting networking permissions
+to the instance. Depending on network (VCN and subnet) setup, this may be
+required for Packer to successfully SSH into the instance. NSGs are a property
+of the virtual network interface card (VNIC) attached to the instance, and
+are listed in `nsg_ids` under `create_vnic_details`. 
+```
+{
+  "name":                "base-image-{{isotime \"20000102030405\"}}",
+  "type":                "oracle-oci",
+  "availability_domain": "aaaa:PHX-AD-1",
+  "base_image_ocid":     "ocid1.image.oc1.iad.aaa",
+  "compartment_ocid":    "ocid1.compartment.oc1..aaa",
+  "image_name":          "my-image-{{isotime \"20000102030405\"}}",
+  "shape":               "VM.Standard.E2.1",
+  "subnet_ocid":         "ocid1.subnet.oc1.iad.aaa",
+  "use_private_ip":      "true",
+  "instance_name":       "packer-build-{{isotime \"20000102030405\"}}",
+  "instance_tags":       { "testing": "yes" },
+  "instance_defined_tags": {
+    "Operations": {
+      "Team": "CostCenter",
+      "Environment": "prod"
+    }
+  }
+  "create_vnic_details": {
+    "assign_public_ip": "false",
+    "display_name": "testing-123",
+    "nsg_ids": ["ocid1.networksecuritygroup.oc1.iad.aaa"]
+  },
+  "tags": {
+    "CreationDate":  "{{isotime \"20000102 15:04:05 MST\"}}"
+  }
+}
+```