[rewrite] Updated backend structure a bit and started working on registration

backend/app/services/user_service.py

@@ -0,0 +1,18 @@
+from app.database.manager import DatabaseManager
+from app.models.user_model import User
+
+from app.schemas.user_register_schema import UserRegisterSchema
+
+
+def create_user(user_data: UserRegisterSchema):
+
+    with DatabaseManager.get_session() as session:
+        user = User(
+            username=user_data.username,
+            password=user_data.password,
+            email=user_data.email,
+            phone_number=user_data.phone_number,
+            shop_id=user_data.shop_id
+        )
+        session.add(user)
+        session.commit()