feat: add core data model

backend/internal/db/db.go

@@ -0,0 +1,10 @@
+package db
+
+import (
+	"gorm.io/driver/postgres"
+	"gorm.io/gorm"
+)
+
+func Open(databaseURL string) (*gorm.DB, error) {
+	return gorm.Open(postgres.Open(databaseURL), &gorm.Config{})
+}