started with postgres installation

configure_postgresql.yml

+---
+- name: configure postgres dbs
+  become: true
+  hosts: all
+  tasks:
+    # enable PostgreSQL service
+    - name: ensure postgres service is enabled and running
+      service:
+        name:postgresql
+        state: started
+        enabled: yes
+
+    # create databases and logins for the users
+    - name: create databases
+      postgresql_db:
+        name: "instance_{{ item.key }}"
+        encoding: "UTF-8"
+        lc_collate: de_DE.UTF-8
+        lc_ctype: de_DE.UTF-8
+        template: "template0"
+        state: present
+      with_dict: "{{ otree_users }}"
+      when: item.value.override
+
+    - name: ensure users have access to the databases
+      postgresql_user:
+        db: "instance_{{ item.key }}"
+        name: "{{ item }}"
+        name: "{{ item }}"
+        priv: ALL
+        state: present
+      with_dict: "{{ otree_users }}"
+      when: item.value.override
+
+    - name: ensure users do not have unnecessary priviliges
+      postgresql_user:
+        role_attr_flags: NOSUPERUSER,NOCREATEDB
+      when: item.value.override

site.yml

@@ -4,6 +4,9 @@
   hosts: all
   vars:
     prereq_packages: 
+      - openssl
+      - libssl-dev
+      - libssl-doc
       - python3-pip 
       - python3-dev
       - python3-venv
@@ -12,7 +15,8 @@
       - git
       - nginx
       - supervisor
-      # maybe add postgresql, postgresql-contriv
+      - postgresql
+      - postgresql-contrib
   tasks:
     # create/delete users as specified in group_vars/otree_users.yml
     - name: Create group for otreeusers
@@ -61,5 +65,6 @@
         state: latest
 
 - import_playbook: "configure_nginx.yml"
+- import_playbook: "configure_postgresql.yml"
 - import_playbook: "setup_otree.yml"
 - import_playbook: "setup_firewall.yml"