- name: Ensure groups exists
  group:
    name: '{{ item }}'
    state: present
  with_items: "{{ user_groups }}"
  when: user_groups is defined   

- name: adding existing user '{{ user }}' to groups
  user:
    groups: '{{ item }}'
    name: user
    append: yes
  with_items: "{{ user_groups }}"
  when: user_groups is defined