role:postfix: add postfix__recipient_canonicals variable

[slalomsk8er]

This would allow to send all local mails to a team mailbox and would make the following playbook obsolete.

---
- name: Configure Postfix canonical maps like Exim rewrites
  hosts: Monitoring:&rpm
  become: yes
  vars:
    sender_canonical_file: /etc/postfix/sender_canonical
    recipient_canonical_file: /etc/postfix/recipient_canonical
    public_domain: example.com
    team_mailbox: monitoring_team

  tasks:

    - name: Ensure postfix-pcre package is installed
      package:
        name: postfix-pcre
        state: present
      tags: postfix

    - name: Create sender_canonical map (user@host.domain -> user_host.domain@{{ public_domain }})
      copy:
        dest: "{{ sender_canonical_file }}"
        content: |
          # Auto-generated sender canonical map
          /^(.+)@{{ inventory_hostname | regex_escape }}$/    ${1}_{{ inventory_hostname }}@{{ public_domain }}
        owner: root
        group: root
        mode: '0644'
      notify: Reload Postfix

    - name: Create recipient_canonical map (inventory_hostname -> {{ team_mailbox }}@{{ public_domain }})
      copy:
        dest: "{{ recipient_canonical_file }}"
        content: |
          # Auto-generated recipient canonical map
          /@{{ inventory_hostname | regex_escape }}$/    {{ team_mailbox }}@{{ public_domain }}
        owner: root
        group: root
        mode: '0644'
      notify: Reload Postfix

    - name: Configure Postfix to use canonical maps
      lineinfile:
        path: /etc/postfix/main.cf
        regexp: '^{{ item.key }} ='
        line: "{{ item.key }} = pcre:{{ item.value }}"
        state: present
      loop:
        - { key: 'sender_canonical_maps', value: "{{ sender_canonical_file }}" }
        - { key: 'recipient_canonical_maps', value: "{{ recipient_canonical_file }}" }
      notify: Reload Postfix

  handlers:
    - name: Reload Postfix
      service:
        name: postfix
        state: reloaded