Add observability platform Ansible project

Deploys the Grafana stack (Prometheus/Alertmanager/Loki/Tempo/Grafana with
Alloy as collector) and the ELK stack (Filebeat/Logstash/Elasticsearch/
Kibana) via Docker Compose on a target host. External to the application
repo, pre-built by the mentor.

ansible/roles/observability/templates/elk-grafana/docker-compose.yml.j2

@@ -0,0 +1,86 @@
+services:
+  elasticsearch:
+    image: docker.elastic.co/elasticsearch/elasticsearch:{{ elastic_version }}
+    restart: unless-stopped
+    environment:
+      discovery.type: single-node
+      xpack.security.enabled: "false"
+      xpack.security.enrollment.enabled: "false"
+      ES_JAVA_OPTS: "-Xms{{ elasticsearch_heap }} -Xmx{{ elasticsearch_heap }}"
+    volumes:
+      - elasticsearch-data:/usr/share/elasticsearch/data
+    ports:
+      - "9200:9200"
+    healthcheck:
+      test: ["CMD-SHELL", "curl -fsS http://localhost:9200/_cluster/health || exit 1"]
+      interval: 10s
+      timeout: 5s
+      retries: 30
+    networks: [observability]
+
+  logstash:
+    image: docker.elastic.co/logstash/logstash:{{ elastic_version }}
+    restart: unless-stopped
+    depends_on:
+      elasticsearch:
+        condition: service_healthy
+    volumes:
+      - ./config/logstash/pipeline:/usr/share/logstash/pipeline:ro
+      - logstash-data:/usr/share/logstash/data
+    ports:
+      - "5044:5044"
+      - "5000:5000/tcp"
+    networks: [observability]
+
+  filebeat:
+    image: docker.elastic.co/beats/filebeat:{{ elastic_version }}
+    user: root
+    restart: unless-stopped
+    command: ["filebeat", "-e", "--strict.perms=false"]
+    depends_on: [logstash]
+    volumes:
+      - ./config/filebeat/filebeat.yml:/usr/share/filebeat/filebeat.yml:ro
+      - /var/lib/docker/containers:/var/lib/docker/containers:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+      - filebeat-data:/usr/share/filebeat/data
+    networks: [observability]
+
+  kibana:
+    image: docker.elastic.co/kibana/kibana:{{ elastic_version }}
+    restart: unless-stopped
+    depends_on:
+      elasticsearch:
+        condition: service_healthy
+    environment:
+      ELASTICSEARCH_HOSTS: http://elasticsearch:9200
+    ports:
+      - "5601:5601"
+    networks: [observability]
+
+  grafana:
+    image: grafana/grafana:{{ grafana_version }}
+    restart: unless-stopped
+    depends_on:
+      elasticsearch:
+        condition: service_healthy
+    environment:
+      GF_SECURITY_ADMIN_USER: "{{ grafana_admin_user }}"
+      GF_SECURITY_ADMIN_PASSWORD: "{{ grafana_admin_password }}"
+      GF_USERS_ALLOW_SIGN_UP: "false"
+    volumes:
+      - grafana-data:/var/lib/grafana
+      - ./config/grafana/provisioning:/etc/grafana/provisioning:ro
+    ports:
+      - "3000:3000"
+    networks: [observability]
+
+volumes:
+  elasticsearch-data:
+  logstash-data:
+  filebeat-data:
+  grafana-data:
+
+networks:
+  observability:
+    driver: bridge
+