Ansible dictionary merge, can be used to allow inventory/hosts/groups to override defaults

main.yml

---
- name: Create PgBouncer configuration
  sudo: true
  ini_file: >
    backup=yes
    dest=/etc/pgbouncer/pgbouncer.ini
    section=pgbouncer
    option="{{ item.key }}"
    value="{{ item.value }}"
    state="{% if item.value != None %}present{% else %}absent{% endif %}"
    owner=postgres group=postgres
    mode=0640
  # Merge pgbouncer_defaults with pgbouncer_configuration
  with_dict: "{% set merged = ( pgbouncer_defaults | default({}) ) %}{% set noop = merged.update( pgbouncer_configuration | default({}) ) %}{{ merged }}"
  notify: restart pgbouncer