Switch away from using with_items for apt uses

roles/common/tasks/main.yml

@@ -16,8 +16,9 @@
   apt_repository: repo="deb https://dl.yarnpkg.com/debian/ stable main" state=present
 # Note that we don't install nginx, letsencrypt, postgresql and redis here, that will be in different roles
 - name: Update apt cache and install various dependencies
-  apt: name={{ item }} state=latest update_cache=yes
-  with_items:
+  apt: name={{ packages }} state=latest update_cache=yes
+  vars:
+    packages:
      - imagemagick
      - ffmpeg
      - libpq-dev

roles/mastodon-postgresql/tasks/main.yml

@@ -3,8 +3,9 @@
 # database user
 
 - name: Install PostgreSQL server and related packages
-  apt: name={{ item }} state=latest update_cache=yes
-  with_items:
+  apt: name={{ packages }} state=latest update_cache=yes
+  vars:
+    packages:
      - postgresql
      - postgresql-contrib
      - python-psycopg2

roles/mastodon-redis/tasks/main.yml

@@ -2,7 +2,8 @@
 # This playbook installs Redis for Mastodon's user
 
 - name: Install redis
-  apt: name={{ item }} state=latest update_cache=yes
-  with_items:
+  apt: name={{ packages }} state=latest update_cache=yes
+  vars:
+    packages:
      - redis-tools
      - redis-server