Add dbx library: PostgreSQL cluster with master/replica routing, retry, health checking

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

options_test.go

@@ -0,0 +1,35 @@
+package dbx
+
+import (
+	"testing"
+	"time"
+)
+
+func TestApplyOptions(t *testing.T) {
+	cfg := Config{}
+
+	logger := nopLogger{}
+	metrics := &MetricsHook{}
+	retry := RetryConfig{MaxAttempts: 7}
+	hc := HealthCheckConfig{Interval: 10 * time.Second}
+
+	ApplyOptions(&cfg,
+		WithLogger(logger),
+		WithMetrics(metrics),
+		WithRetry(retry),
+		WithHealthCheck(hc),
+	)
+
+	if cfg.Logger == nil {
+		t.Error("Logger should be set")
+	}
+	if cfg.Metrics == nil {
+		t.Error("Metrics should be set")
+	}
+	if cfg.Retry.MaxAttempts != 7 {
+		t.Errorf("Retry.MaxAttempts = %d, want 7", cfg.Retry.MaxAttempts)
+	}
+	if cfg.HealthCheck.Interval != 10*time.Second {
+		t.Errorf("HealthCheck.Interval = %v, want 10s", cfg.HealthCheck.Interval)
+	}
+}