## Feature Description
The `model-router` plugin implements routing functionality based on the model parameter in LLM protocols.

## Configuration Fields

| Name                 | Data Type        | Requirement               | Default Value            | Description                                                  |
| -----------          | --------------- | ----------------------- | ------                   | -------------------------------------------           |
| `modelKey`           | string          | Optional                | model                    | Location of the model parameter in the request body          |
| `addProviderHeader`  | string          | Optional                | -                        | Which request header to add the provider name parsed from the model parameter |
| `modelToHeader`      | string          | Optional                | -                        | Which request header to directly add the model parameter to  |
| `enableOnPathSuffix` | array of string | Optional                | ["/v1/chat/completions"] | Only effective for requests with these specific path suffixes, can be configured as "*" to match all paths |

## Runtime Properties

Plugin execution phase: Authentication phase
Plugin execution priority: 900

## Effect Description

### Routing Based on Model Parameter

The following configuration is needed:

```yaml
modelToHeader: x-higress-llm-model
```

The plugin extracts the model parameter from the request and sets it to the x-higress-llm-model request header for subsequent routing. For example, the original LLM request body is:

```json
{
    "model": "qwen-long",
    "frequency_penalty": 0,
    "max_tokens": 800,
    "stream": false,
    "messages": [{
        "role": "user",
        "content": "What is the GitHub address of the Higress project's main repository?"
    }],
    "presence_penalty": 0,
    "temperature": 0.7,
    "top_p": 0.95
}
```

After processing by this plugin, the following request header will be added (can be used for route matching):

x-higress-llm-model: qwen-long

### Extracting Provider Field from Model Parameter for Routing

> Note that this mode requires the client to specify the provider in the model parameter using the `/` delimiter

The following configuration is needed:

```yaml
addProviderHeader: x-higress-llm-provider
```

The plugin extracts the provider part (if any) from the model parameter in the request, sets it to the x-higress-llm-provider request header for subsequent routing, and rewrites the model parameter to only contain the model name part. For example, the original LLM request body is:

```json
{
    "model": "dashscope/qwen-long",
    "frequency_penalty": 0,
    "max_tokens": 800,
    "stream": false,
    "messages": [{
        "role": "user",
        "content": "What is the GitHub address of the Higress project's main repository?"
    }],
    "presence_penalty": 0,
    "temperature": 0.7,
    "top_p": 0.95
}
```

After processing by this plugin, the following request header will be added (can be used for route matching):

x-higress-llm-provider: dashscope

The original LLM request body will be changed to:

```json
{
    "model": "qwen-long",
    "frequency_penalty": 0,
    "max_tokens": 800,
    "stream": false,
    "messages": [{
        "role": "user",
        "content": "What is the GitHub address of the Higress project's main repository?"
    }],
    "presence_penalty": 0,
    "temperature": 0.7,
    "top_p": 0.95
}