### What problem does this PR solve?

Previous:
- Defaulted to hardcoded model 'BAAI/bge-large-zh-v1.5@BAAI'
- Did not respect user-configured default embedding_model

Now:
- Correctly prioritizes user-configured default embedding_model

Other:
- Make embedding_model optional in CreateDatasetReq with proper None
handling
- Add default embedding model fallback in dataset update when empty
- Enhance validation utils to handle None values and string
normalization
- Update SDK default embedding model to None to match API changes
- Adjust related test cases to reflect new validation rules

### Type of change

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

### What problem does this PR solve?

1. rename var
2. update if statement

### Type of change

- [x] Refactoring

---------

Signed-off-by: Jin Hai <haijin.chn@gmail.com>
Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

### What problem does this PR solve?

- Add filename length validation (<=255 bytes) for document
upload/rename in both HTTP and SDK APIs
- Update error messages for consistency
- Fix comparison operator in SDK from '>=' to '>' for filename length
check

### Type of change

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

### What problem does this PR solve?

- Implement RAGFlowWebApiAuth class for web API authentication
- Add comprehensive test cases for KB CRUD operations
- Set up common fixtures and utilities in conftest.py
- Add helper functions in common.py for web API requests

The changes establish a complete testing framework for knowledge base
management via web API endpoints.

### Type of change

- [x] Add test case

### What problem does this PR solve?

- Remove pagerank from CreateDatasetReq and add to UpdateDatasetReq
- Add pagerank update logic in dataset update endpoint
- Update API documentation to reflect changes
- Modify related test cases and SDK references

#8208

This change makes pagerank a mutable property that can only be set after
dataset creation, and only when using elasticsearch as the doc engine.

### Type of change

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

### What problem does this PR solve?

- Update chat assistant tests to use dataset.id directly in payloads
- Enhance document parsing tests with better condition checking
- Add explicit type hints and improve timeout handling

Action_7556

### Type of change

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

### What problem does this PR solve?

- Consolidate HTTP API test fixtures using batch operations
(batch_add_chunks, batch_create_chat_assistants)
- Fix fixture initialization order in clear_session_with_chat_assistants
- Add new SDK API test suite for session management
(create/delete/list/update)

### Type of change

- [x] Add test cases
- [x] Refactoring

### What problem does this PR solve?

- Implement new SDK API test cases for chat assistant CRUD operations
- Enhance HTTP API concurrent tests to use as_completed for better
reliability

### Type of change

- [x] Add test cases
- [x] Refactoring

### What problem does this PR solve?

- Improve concurrent test cases by using as_completed for better
reliability
- Rename variables for clarity (chunk_num -> count)
- Add new SDK API test suite for chunk management operations
- Update HTTP API tests with consistent concurrency patterns

### Type of change

- [x] Add test cases
- [x] Refactoring

### What problem does this PR solve?

Add sdk document test cases

### Type of change

- [x] Add test cases

### What problem does this PR solve?

Add sdk dataset test cases

### Type of change

- [x] Add test case