### What problem does this PR solve?

https://github.com/infiniflow/ragflow/issues/9385
Based on my understanding, I think checking empty string is fine

### Type of change

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

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

### What problem does this PR solve?

#9082 #6365

### Type of change

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

### What problem does this PR solve?

#9082 #6365

<u> **WARNING: it's not compatible with the older version of `Agent`
module, which means that `Agent` from older versions can not work
anymore.**</u>

### Type of change

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

### What problem does this PR solve?
```
Invoke agent
To be able to interact dynamically with the API, there is a customizable Data Type JSON or FormData, the default is JSON 
```

### Type of change

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

---------

Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

### What problem does this PR solve?
Invoke component can be used to call third party services.
Tried GET/POST/PUT from web UI, and found PUT request failed like this:
(test api: api/v1/chats/<assistant_id>)
 ```
{"code":100,"data":null,"message":"AttributeError("'NoneType' object has
no attribute 'get'")"}
```

Root cause: Invoke PUT with a 'data=args' parameter, which is a form-encoded data, however the default content type setting of request header is application/json. The test api could not deal with such case.

Fix: use the 'json' parameter of reqeusts.put(), same as Invoke POST. Do not use the 'data' parameter.
Another way is to use 'data=json.dumps(args)'.

### Type of change

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

### What problem does this PR solve?

fix bug, agent invoke can not get params from begin

### Type of change

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

Co-authored-by: wangrui <wangrui@haima.me>

### What problem does this PR solve?

to fixed issue https://github.com/infiniflow/ragflow/issues/4236

### Type of change

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

### What problem does this PR solve?


### Type of change

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

### What problem does this PR solve?

#2834 
### Type of change

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

### What problem does this PR solve?

#2908

### Type of change

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