feat: configure Mattermost webhook integrations

Added Mattermost webhook notifications for infrastructure services:

- **Netdata**: Health monitoring alerts sent to Mattermost
  - Configured via MATTERMOST_WEBHOOK_URL environment variable
  - All alert roles route to Mattermost notifications channel

- **Restic/Backrest**: Backup status notifications
  - Webhook URL passed as environment variable
  - Backrest web UI can be configured to use the webhook

- **Watchtower**: Container update notifications
  - Uses Shoutrrr mattermost:// URL format
  - Sends notifications when containers are updated

Configuration:
- Webhook URL stored securely in .env file
- All services reference ${MATTERMOST_WEBHOOK_URL} variable
- Watchtower uses specialized Shoutrrr format URL

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

arty.yml

@@ -163,6 +163,7 @@ envs:
     WATCHTOWER_RUN_ONCE: false
     WATCHTOWER_LOG_LEVEL: info
     WATCHTOWER_ROLLING_RESTART: false
+    WATCHTOWER_NOTIFICATIONS: mattermost
 
 scripts:
   config: docker compose config

netdata/compose.yaml

@@ -33,6 +33,7 @@ services:
       - NETDATA_CLAIM_TOKEN=${NETDATA_CLAIM_TOKEN:-}
       - NETDATA_CLAIM_URL=${NETDATA_CLAIM_URL:-}
       - NETDATA_CLAIM_ROOMS=${NETDATA_CLAIM_ROOMS:-}
+      - MATTERMOST_WEBHOOK_URL=${MATTERMOST_WEBHOOK_URL:-}
     networks:
       - compose_network
     labels:

netdata/health_alarm_notify.conf

@@ -24,3 +24,24 @@ role_recipients_email[dba]="${ADMIN_EMAIL}"
 role_recipients_email[webmaster]="${ADMIN_EMAIL}"
 role_recipients_email[proxyadmin]="${ADMIN_EMAIL}"
 role_recipients_email[sitemgr]="${ADMIN_EMAIL}"
+
+###############################################################################
+# Mattermost notifications
+###############################################################################
+
+# Enable Mattermost notifications
+SEND_MATTERMOST="YES"
+
+# Mattermost incoming webhook URL
+MATTERMOST_WEBHOOK_URL="${MATTERMOST_WEBHOOK_URL}"
+
+# Mattermost channel (optional, webhook default channel will be used if empty)
+DEFAULT_RECIPIENT_MATTERMOST=""
+
+# Mattermost notification recipients per role
+role_recipients_mattermost[sysadmin]="notifications"
+role_recipients_mattermost[domainadmin]="notifications"
+role_recipients_mattermost[dba]="notifications"
+role_recipients_mattermost[webmaster]="notifications"
+role_recipients_mattermost[proxyadmin]="notifications"
+role_recipients_mattermost[sitemgr]="notifications"

restic/compose.yaml

@@ -38,6 +38,7 @@ services:
       BACKREST_CONFIG: /config/config.json
       XDG_CACHE_HOME: /cache
       TMPDIR: /tmp
+      MATTERMOST_WEBHOOK_URL: ${MATTERMOST_WEBHOOK_URL:-}
 
     networks:
       - compose_network