Issue deserializing RunSteps for file search

[averyaube]

Description

I have an assistant that uses the file search tool. When attempting to analyze the steps after a run, I receive the following error:

com.aallam.openai.api.exception.OpenAIHttpException: Illegal input: Serializer for subclass 'file_search' is not found in the polymorphic scope of 'ToolCallStep'.
Check if class with serial name 'file_search' exists and serializer is registered in a corresponding SerializersModule.
To be registered automatically, class 'file_search' has to be '@Serializable', and the base class 'ToolCallStep' has to be sealed and '@Serializable'.
JSON input: .....ousing act design manual.pdf","score":0.2420911092145576}]}}

Steps to Reproduce

1. Create an assistant with the file_search tool enabled / a relevant VectorStore provided.
2. Execute an assistant Run with a message that will trigger a file search
3. Wait until the Run is completed
4. Attempt to iterate through the run steps:

// It's possible the exception is thrown during this call and we don't even
// get to the step iteration below
val steps = client.runSteps(
    threadId = threadId,
    runId = run.id,
)

for (step in steps) {
    when (step.stepDetails) {
        is MessageCreationStepDetails -> {
            // I was extracting message content here     
        }
        else -> {}
    }
}

Environment

• openai-kotlin version: 4.0.0-beta01
• Kotlin version: 2.1.0
• OS: Manjaro Linux

Additional Info

It seems like an additional subclass of ToolCallStep needs to be implemented for file search steps.