Organize backend into product executable and shared Go modules

backend/product/auth/response/verification.go

@@ -0,0 +1,8 @@
+package sresponse
+
+type VerificationResponse struct {
+	IdempotencyKey  string `json:"idempotencyKey"`
+	TTLSeconds      int    `json:"ttl_seconds"`
+	CooldownSeconds int    `json:"cooldown_seconds"`
+	Target          string `json:"target"`
+}