### What problem does this PR solve?

Change mcp_client module to rag/utils/conn.

### Type of change

- [x] Refactoring

### What problem does this PR solve?

This is a cherry-pick from #7781 as requested.

### 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?

Hello, our use case requires LLM agent to invoke some tools, so I made a
simple implementation here.

This PR does two things:

1. A simple plugin mechanism based on `pluginlib`:

This mechanism lives in the `plugin` directory. It will only load
plugins from `plugin/embedded_plugins` for now.

A sample plugin `bad_calculator.py` is placed in
`plugin/embedded_plugins/llm_tools`, it accepts two numbers `a` and `b`,
then give a wrong result `a + b + 100`.

In the future, it can load plugins from external location with little
code change.

Plugins are divided into different types. The only plugin type supported
in this PR is `llm_tools`, which must implement the `LLMToolPlugin`
class in the `plugin/llm_tool_plugin.py`.
More plugin types can be added in the future.

2. A tool selector in the `Generate` component:

Added a tool selector to select one or more tools for LLM:


![image](https://github.com/user-attachments/assets/74a21fdf-9333-4175-991b-43df6524c5dc)

And with the `bad_calculator` tool, it results this with the `qwen-max`
model:


![image](https://github.com/user-attachments/assets/93aff9c4-8550-414a-90a2-1a15a5249d94)


### Type of change

- [ ] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

Co-authored-by: Yingfeng <yingfeng.zhang@gmail.com>

### What problem does this PR solve?

This pull request implements the feature mentioned in #3322. 

Instead of manually having to edit the `service_conf.yaml` file when
changes have been made to `.env` and mapping it into the docker
container at runtime, a template file is used and the values replaced by
the environment variables from the `.env` file when the container is
started.
 

### Type of change

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

---------

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

### What problem does this PR solve?

feat: Delete http_api_reference.md from  api folder #1102

### Type of change

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

### What problem does this PR solve?

added back oc9

### Type of change

- [x] Refactoring

### What problem does this PR solve?

Fix docker file bugs

### Type of change

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

---------

Co-authored-by: writinwaters <93570324+writinwaters@users.noreply.github.com>
Co-authored-by: Kevin Hu <kevinhu.sh@gmail.com>

### What problem does this PR solve?

Related source file is in Windows/DOS format, they are format to Unix
format.

### Type of change

- [x] Refactoring

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

### What problem does this PR solve?

### Type of change

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

### What problem does this PR solve?


### Type of change

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

### What problem does this PR solve?

#1164 

### Type of change

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

### Type of change

- [x] Refactoring

### What problem does this PR solve?

This PR aims to add support for running Ragflow on Docker with the
OpenCloudOS 9 distribution.

### Type of change

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

Co-authored-by: edwardewang <edwardewang@tencent.com>

### What problem does this PR solve?

issue: #205 

### Type of change

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