make postgres password optional

defaults/main.yml

@@ -52,8 +52,8 @@ postgres_podman_args:
 postgres_log_level: warning
 
 postgres_user: postgres
-postgres_password: postgres
-postgres_db: postgres
+# @var postgres_password:description: Password of the superuser defined in `postgres_user`.
+# postgres_password:value: $ "_unset_"
 
 # @var postgres_app_user:description: >
 # Application user name without superuser privileges. Full access to `postgres_db`
@@ -63,10 +63,11 @@ postgres_db: postgres
 # @var postgres_app_password:description: Application user password.
 # @var postgres_app_password:value: $ "_unset_"
 
+postgres_db: postgres
+
 postgres_host_auth_method: scram-sha-256
 postgres_initdb_args:
   - --auth-host=scram-sha-256
-  - --auth-local=scram-sha-256
 
 postgres_tls_enabled: False
 postgres_tls_ca_file: "/var/lib/postgresql/tls/CA.pem"

templates/etc/containers/systemd/postgres.env.j2

@@ -1,7 +1,9 @@
 #jinja2: lstrip_blocks: True
 {{ ansible_managed | comment }}
 POSTGRES_USER={{ postgres_user }}
+{% if postgres_password is defined %}
 POSTGRES_PASSWORD={{ postgres_password }}
+{% endif %}
 {% if postgres_app_user is defined and postgres_app_password is defined %}
 POSTGRES_APP_USER={{ postgres_app_user }}
 POSTGRES_APP_PASSWORD={{ postgres_app_password }}