feat: support pdf files in Prompt

[konrad-czarnota-ds]

Feature description

I would like to be able to attach .pdf files to prompts in ragbits and use them when chatting with LLM. Here's a quick and dirty solution that I did to make it work that needs to be polished:

import base64
from pydantic import BaseModel
from ragbits.core.prompt import Prompt


class InstructionExtractionPromptInput(BaseModel):
    pdf_path: str


class InstructionExtractionPromptOutput(BaseModel):
    instructions: str


class InstructionExtractionPrompt(Prompt[InstructionExtractionPromptInput, InstructionExtractionPromptOutput]):
    user_prompt = """
    """

    image_input_fields = ["pdf_path"]

    @staticmethod
    def _create_message_with_image(image: str | bytes) -> dict:
        if type(image) == str and image.endswith(".pdf"):
            with open(image, "rb") as f:
                data = f.read()

            base64_string = base64.b64encode(data).decode("utf-8")

            return{
                        "type": "file",
                        "file": {
                            "filename": "instruction.pdf",
                            "file_data": f"data:application/pdf;base64,{base64_string}",
                        }
                    }
        else:
            return super()._create_message_with_image(image)

Motivation

LiteLLM supports files passing through API, I think ragbits should too as this might be necessary to handle different documents

Additional context

No response