Add rag module: Spring AI 2.0 RAG with pgvector, chunking, reranking and a faithfulness check

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01B38FGKKam5SCGgwgduVAh3

rag/docker-compose.yml

@@ -0,0 +1,21 @@
+# PostgreSQL 16 with the pgvector extension. init.sql runs once, on the first start of an empty volume.
+services:
+  postgres:
+    image: pgvector/pgvector:pg16
+    environment:
+      POSTGRES_DB: ragdb
+      POSTGRES_USER: raguser
+      POSTGRES_PASSWORD: ragpass
+    ports:
+      - "5432:5432"
+    volumes:
+      - ./init.sql:/docker-entrypoint-initdb.d/init.sql:ro
+      - pgdata:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U raguser -d ragdb"]
+      interval: 5s
+      timeout: 3s
+      retries: 10
+
+volumes:
+  pgdata: