---
- name: Add Prosody key
  apt_key:
    id: 74D9DBB5
    url: https://prosody.im/files/prosody-debian-packages.key
- name: Add Prosody repository
  apt_repository:
    repo: 'deb http://packages.prosody.im/debian {{ ansible_lsb.codename }} main'
- name: Pin packages
  copy:
    src: etc/apt/preferences.d/prosody
    dest: /etc/apt/preferences.d/prosody
...