### What problem does this PR solve?

Add license statement.

### Type of change

- [x] Refactoring

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

### What problem does this PR solve?

Update displayed_name to display_name

### Type of change

- [x] Refactoring

Co-authored-by: liuhua <10215101452@stu.ecun.edu.cn>

### What problem does this PR solve?

Add tests for frontend API

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

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Co-authored-by: liuhua <10215101452@stu.ecun.edu.cn>

### What problem does this PR solve?

Add test for API

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

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Co-authored-by: liuhua <10215101452@stu.ecun.edu.cn>
Co-authored-by: Zhichang Yu <yuzhichang@gmail.com>

### What problem does this PR solve?

Add test for CI

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

Co-authored-by: liuhua <10215101452@stu.ecun.edu.cn>

### What problem does this PR solve?

Manage ragflow-sdk with poetry
### Type of change

- [x] Refactoring

### What problem does this PR solve?

Fix some issues in API and test

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

Co-authored-by: liuhua <10215101452@stu.ecun.edu.cn>

### What problem does this PR solve?

Test Cases

### Type of change

- [x] Refactoring

Co-authored-by: liuhua <10215101452@stu.ecun.edu.cn>

### What problem does this PR solve?

Fix some issues in API

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

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Co-authored-by: liuhua <10215101452@stu.ecun.edu.cn>

### What problem does this PR solve?

Refactor Chat API

### Type of change

- [x] Refactoring

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Co-authored-by: liuhua <10215101452@stu.ecun.edu.cn>