### 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?

Fix potential SSRF attack vulnerability

### 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?



### Type of change


- [x] Performance Improvement

### What problem does this PR solve?


### Type of change

- [x] Refactoring

### What problem does this PR solve?

Knowledge base management supports crawling information from web pages
and generating PDF documents

### Type of change
- [x] New Feature (Support document from web pages)