Add telegraf_output selector for InfluxDB/Postgres dual-write

Introduces global.telegraf_output (INFLUXDB|POSTGRES|BOTH, default BOTH)
so Telegraf can write metrics to Postgres alongside or instead of
InfluxDB. Each minion authenticates with its own so_telegraf_<minion>
role and writes to a matching schema inside a shared so_telegraf
database, keeping blast radius per-credential to that minion's data.

- Per-minion credentials auto-generated and persisted in postgres/auth.sls
- postgres/telegraf_users.sls reconciles roles/schemas on every apply
- Firewall opens 5432 only to minion hostgroups when Postgres output is active
- Reactor on salt/auth + orch/telegraf_postgres_sync.sls provision new
  minions automatically on key accept
- soup post_to_3.1.0 backfills users for existing minions on upgrade
- so-show-stats prints latest CPU/mem/disk/load per minion for sanity checks
- so-telegraf-trim + nightly cron prune rows older than
  postgres.telegraf.retention_days (default 14)

salt/postgres/telegraf_users.sls

@@ -0,0 +1,49 @@
+# Copyright Security Onion Solutions LLC and/or licensed to Security Onion Solutions LLC under one
+# or more contributor license agreements. Licensed under the Elastic License 2.0 as shown at
+# https://securityonion.net/license; you may not use this file except in compliance with the
+# Elastic License 2.0.
+
+{% from 'allowed_states.map.jinja' import allowed_states %}
+{% if sls.split('.')[0] in allowed_states %}
+{%   from 'vars/globals.map.jinja' import GLOBALS %}
+
+{% set TG_OUT = (GLOBALS.telegraf_output | default('INFLUXDB')) | upper %}
+{% if TG_OUT in ['POSTGRES', 'BOTH'] %}
+
+{%   set users = salt['pillar.get']('postgres:auth:users', {}) %}
+{%   for key, entry in users.items() %}
+{%     if key.startswith('telegraf_') and entry.get('user') and entry.get('pass') %}
+{%       set u = entry.user %}
+{%       set p = entry.pass | replace("'", "''") %}
+
+postgres_telegraf_role_{{ u }}:
+  cmd.run:
+    - name: |
+        docker exec -i so-postgres psql -v ON_ERROR_STOP=1 -U postgres -d so_telegraf <<'EOSQL'
+        DO $$
+        BEGIN
+            IF NOT EXISTS (SELECT FROM pg_catalog.pg_roles WHERE rolname = '{{ u }}') THEN
+                EXECUTE format('CREATE ROLE %I WITH LOGIN PASSWORD %L', '{{ u }}', '{{ p }}');
+            ELSE
+                EXECUTE format('ALTER ROLE %I WITH PASSWORD %L', '{{ u }}', '{{ p }}');
+            END IF;
+        END
+        $$;
+        GRANT CONNECT ON DATABASE so_telegraf TO "{{ u }}";
+        CREATE SCHEMA IF NOT EXISTS "{{ u }}" AUTHORIZATION "{{ u }}";
+        EOSQL
+    - require:
+      - docker_container: so-postgres
+
+{%     endif %}
+{%   endfor %}
+
+{% endif %}
+
+{% else %}
+
+{{sls}}_state_not_allowed:
+  test.fail_without_changes:
+    - name: {{sls}}_state_not_allowed
+
+{% endif %}