docs(bootstrap): fix users dict format in examples, sync schema defaults, document secure_boot/rhel_repo

inventory_baremetal_example.yml

@@ -9,8 +9,11 @@ all:
     baremetal01.example.com:
       ansible_host: 10.0.0.162
       ansible_user: root
-      ansible_password: "1234"
-      ansible_become_password: "1234"
+      ansible_password: "CHANGE_ME"
+      ansible_become_password: "CHANGE_ME"
+      # Required for physical installs: confirms the operator accepts that
+      # install_drive will be wiped. system_check refuses to run without it.
+      physical_install_confirmed: true
       system:
         type: "physical"
         os: "archlinux"
@@ -18,3 +21,10 @@ all:
         disks:
           - device: "/dev/sda"
             size: 120
+        users:
+          admin:
+            password: "CHANGE_ME"
+            keys:
+              - "ssh-ed25519 AAAA..."
+        root:
+          password: "CHANGE_ME"