### What problem does this PR solve?
Add two API in go
```
/api/v1/agents/test_db_connection POST
/api/v1/agents/<agent_id>/sessions DELETE
```
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
---------
Co-authored-by: Yingfeng <yingfeng.zhang@gmail.com>
### What problem does this PR solve?
As Title
Codes were tested by Postman
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Go cli
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
---------
Signed-off-by: Jin Hai <haijin.chn@gmail.com>
### What problem does this PR solve?
Fix: Enhanced user management functionality and cascading data deletion.
Added tenant and related data initialization functionality during user
creation, including tenants, user-tenant relationships, LLM
configuration, and root folder.
Added cascading deletion logic for user deletion, ensuring that all
associated data is cleaned up simultaneously when a user is deleted.
Implemented a Werkzeug-compatible password hash algorithm (scrypt) and
verification functionality.
Added multiple DAO methods to support batch data operations and
cascading deletion.
Improved user login processing and added token signing functionality.
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
