feat: enhance configuration with database connection settings and pool tuning

[Baskarayelu]

Summary

• Add PostgreSQL connection pooling and a shared client helper.
• Enhance /api/health to reflect database connectivity (ok vs degraded).
• Document DATABASE_URL and pool tuning environment variables.

Details

• Config & pooling

  • Extend config to include:
    • databaseUrl (from DATABASE_URL, with a local default).
    • dbPool options derived from env vars:
      • DB_POOL_MAX
      • DB_IDLE_TIMEOUT_MS
      • DB_CONN_TIMEOUT_MS
  • Update db.ts to:
    • Instantiate a shared pg.Pool using the centralized config.
    • Export a query(text, params?) helper for simple one-off queries.
    • Add checkDbHealth() which executes SELECT 1 and returns { ok, error? }, logging failures if the DB is unavailable.

• Health endpoint

  • Update HealthResponse in types/index.ts to:
    • Use status: 'ok' | 'degraded'.
    • Include a db object: { status: 'ok' | 'error', error?: string }.
  • Update /api/health (router) to:
    • Call checkDbHealth() on each request.
    • Return status: "ok" when the DB is reachable.
    • Return status: "degraded" and db.status: "error" (with error message) when the DB is down or misconfigured.

• Environment documentation

  • Add .env.example documenting:
    • PORT, NODE_ENV.
    • DATABASE_URL with an example that matches docker-compose and a local default.
    • Optional pool tuning knobs: DB_POOL_MAX, DB_IDLE_TIMEOUT_MS, DB_CONN_TIMEOUT_MS.

Configuration

• Required

  • DATABASE_URL must point to a reachable PostgreSQL instance.

• Optional

  • DB_POOL_MAX – max clients in pool (default: 10).
  • DB_IDLE_TIMEOUT_MS – idle client lifetime in ms (default: 30000).
  • DB_CONN_TIMEOUT_MS – acquire timeout in ms (default: 2000).

Test Plan

• Health with DB up

  • Start Postgres (e.g. docker-compose up).
  • Set a valid DATABASE_URL.
  • GET /api/health → 200 with:
    • status: "ok"
    • db: { status: "ok" }

• Health with DB down

  • Stop Postgres or point DATABASE_URL at an unavailable host.
  • GET /api/health → 200 with:
    • status: "degraded"
    • db: { status: "error", error: "<message>" }
      closes Set Up PostgreSQL and Connection Pool #6
      Closes Add Wallet Authentication (Stellar Address Verification) #18
      Closes Add Vault Balance Check Middleware (Pre-Call) #23
      Closes Add REST Route: List Public APIs (Marketplace) #27

[greatest0fallt1me]

LGTM!