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

inventory_libvirt_example.yml

@@ -6,7 +6,6 @@ all:
       url: "localhost"
       username: ""
       password: ""
-      host: ""
       storage: "default"
     boot_iso: "/var/lib/libvirt/images/archlinux-x86_64.iso"
   children:
@@ -40,7 +39,7 @@ all:
                   path: /var/www
                   fstype: xfs
             users:
-              - name: "web"
+              web:
                 password: "CHANGE_ME"
                 keys:
                   - "ssh-ed25519 AAAA..."
@@ -82,7 +81,7 @@ all:
                   path: /data
                   fstype: ext4
             users:
-              - name: "db"
+              db:
                 password: "CHANGE_ME"
                 keys:
                   - "ssh-ed25519 AAAA..."
@@ -123,7 +122,7 @@ all:
                   path: /data
                   fstype: btrfs
             users:
-              - name: "compute"
+              compute:
                 password: "CHANGE_ME"
                 keys:
                   - "ssh-ed25519 AAAA..."