Explicitly set compartmentID for User, Group and Compartment resources in Identity example

* describe `enable_delete` behavior for Compartment resource in notes

Author: ccushing

docs/examples/identity/compartment.tf

@@ -2,13 +2,14 @@
  * This example file shows how to create a compartment or reference an existing compartment as a resource.
  *
  * Note: the compartment resource internally resolves name collisions and returns a reference to the preexisting
- * compartment. Compartments can not be deleted, so removing a compartment resource from your .tf file will only
- * remove it from your statefile.
+ * compartment by default. Use `enable_delete` to allow compartment deletion and prevent implicitly importing compartments.
  */
 
 resource "oci_identity_compartment" "compartment1" {
   name        = "tf-example-compartment"
   description = "compartment created by terraform"
+  compartment_id = "${var.tenancy_ocid}"
+  enable_delete = false // true will cause this compartment to be deleted when running `terrafrom destroy`
 }
 
 data "oci_identity_compartments" "compartments1" {

docs/examples/identity/group.tf

@@ -5,6 +5,7 @@
 resource "oci_identity_group" "group1" {
   name        = "tf-example-group"
   description = "group created by terraform"
+  compartment_id = "${var.tenancy_ocid}"
 }
 
 resource "oci_identity_user_group_membership" "user-group-mem1" {

docs/examples/identity/user.tf

@@ -5,6 +5,7 @@
 resource "oci_identity_user" "user1" {
   name        = "tf-example-user"
   description = "user created by terraform"
+  compartment_id = "${var.tenancy_ocid}"
 }
 
 data "oci_identity_users" "users1" {