Fix exception handler for proxy server

[AllentDan]

No description provided.

[lvhan028]

We'd better log each request, include add, remove, v1/chat/completions, v1/compeltions
Logging key events within the lifecycle of a request is extremely beneficial for our debugging process.

@app.post('/nodes/add', dependencies=[Depends(check_api_key)])
def add_node(node: Node, raw_request: Request = None):
    """Add a node to the manager.

    - url (str): A http url. Can be the url generated by
        `lmdeploy serve api_server`.
    - status (Dict): The description of the node. An example:
        {models: ['internlm-chat-7b],  speed: 1}. The speed here can be
        RPM or other metric. All the values of nodes should be the same metric.
    """
    try:
        logger.info(f'try to add node {node.url}, {node.status}')
        res = node_manager.add(node.url, node.status)
        if res is not None:
            logger.error(f'add node {node.url} failed, {res}'
            return res
        logger.info(f'add node {node.url} successfully')
        return f'add node {node.url} successfully'
    except:  # noqa
        return f'Failed to add, node {node.url} please check the input url.'

[RunningLeon]

LGTM