wip: prepare arguments for tool call

[eyurtsev]

from langgraph.config import get_config

# Define the prepare_arguments function
def prepare_arguments(tool, arguments: dict) -> dict:
    config = get_config()['configurable']
    user_id = config.get("user_id")
    arguments["_meta"] = {"user_id": user_id}
    return arguments


tools = load_mcp_tools(..., prepare_arguments=prepare_arguments)