Organize backend into product executable and shared Go modules

backend/shared/database/record/ref.go

@@ -0,0 +1,11 @@
+package storable
+
+import "go.mongodb.org/mongo-driver/v2/bson"
+
+const (
+	RefField = "ref"
+)
+
+type Ref struct {
+	Ref bson.ObjectID `bson:"ref" json:"ref"`
+}