Make first integration test

[nao1215]

We will create integration tests with reference to the following README file.
These tests will verify that SQL statements which join or update multiple files work correctly.

filesql/testdata/company/README.md

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	#### **user.csv**
	* **id**: User ID (Primary Key)
	* **name**: User name
	* **email**: Email address
	* **age**: Age (nullable)
	* **department\_id**: Department ID (FK → `department.csv`)
	#### **department.csv**
	* **id**: Department ID (Primary Key)
	* **name**: Department name
	* **location**: Location (nullable)
	#### **orders.csv**
	* **id**: Order ID (Primary Key)
	* **user\_id**: User ID (FK → `user.csv`)
	* **amount**: Order amount
	* **status**: Order status (`pending`, `shipped`, `delivered`, nullable)
	* **created\_at**: Creation timestamp
	#### **address.csv**
	* **id**: Address ID (Primary Key)
	* **user\_id**: User ID (FK → `user.csv`)
	* **address**: Address (nullable)
	* **postal\_code**: Postal code (nullable)
	#### **salary.csv**
	* **id**: Salary ID (Primary Key)
	* **user\_id**: User ID (FK → `user.csv`)
	* **base\_salary**: Base salary
	* **bonus**: Bonus (nullable)
	#### **project.csv**
	* **id**: Project ID (Primary Key)
	* **name**: Project name
	* **department\_id**: Department ID (FK → `department.csv`)
	* **budget**: Project budget (nullable)
	#### **user\_project.csv**
	* **id**: Relation ID (Primary Key)
	* **user\_id**: User ID (FK → `user.csv`)
	* **project\_id**: Project ID (FK → `project.csv`)
	* **role**: Role in project (`manager`, `developer`, `tester`, nullable)
	#### **attendance.csv**
	* **id**: Attendance record ID (Primary Key)
	* **user\_id**: User ID (FK → `user.csv`)
	* **date**: Attendance date
	* **status**: Attendance status (`present`, `absent`, `remote`, nullable)
	#### **performance.csv**
	* **id**: Performance record ID (Primary Key)
	* **user\_id**: User ID (FK → `user.csv`)
	* **year**: Year of evaluation
	* **rating**: Performance rating (1–5, nullable)
	#### **training.csv**
	* **id**: Training ID (Primary Key)
	* **title**: Training title
	* **department\_id**: Department ID (FK → `department.csv`)
	* **duration\_days**: Training duration in days
	#### **user\_training.csv**
	* **id**: Relation ID (Primary Key)
	* **user\_id**: User ID (FK → `user.csv`)
	* **training\_id**: Training ID (FK → `training.csv`)
	* **completed**: Completion status (true/false, nullable)
	#### **benefits.csv**
	* **id**: Benefits record ID (Primary Key)
	* **user\_id**: User ID (FK → `user.csv`)
	* **health\_insurance**: Health insurance enrollment (true/false, nullable)
	* **pension\_plan**: Pension plan enrollment (true/false, nullable)

[nao1215]

#43