used 'product' filter to avoid nested loop for host/group server address and SSH public key paths

roles/init-server/tasks/spawn.yml

@@ -89,18 +89,16 @@
           vars:
             ansible_user: root
           loop: "{{ groups[instance] | default(hostvars[instance]) }}"
-    # @TODO find way to incorporate use of 'groups[instance] | default(hostvars[instance]' for 
-    # looping without loop nesting in below task
     - name: Providing authorized keys for server root account
-      delegate_to: "{{ (groups[instance] | default(hostvars[instance]))[0] }}"
+      delegate_to: "{{ item[0] }}"
       delegate_facts: true
       remote_user: root
       ansible.posix.authorized_key:
         user: "{{ ansible_user }}"
-        key: "{{ lookup('file', item) }}"
+        key: "{{ lookup('file', item[1]) }}"
         state: present
       vars:
         ansible_user: root
-      loop: "{{ root_pubkey_paths }}"
+      loop: "{{ (groups[instance] | default(hostvars[instance])) | product(root_pubkey_paths) }}"
   tags:
     - lan