Fixes image type, adds document type for ChatBedrockConverse

[3coins]

Description

This PR fixes the image type supported by Bedrock Anthropic and other models. It also adds a new type for supporting documents.

Image sample code

from langchain_core.messages import HumanMessage
from langchain_aws import ChatBedrock

llm = ChatBedrock(
    model_id="anthropic.claude-3-sonnet-20240229-v1:0",
    beta_use_converse_api=True
)

# Convert image to bytes
image_path = "images/random-image.jpg"
image_bytes = None
with open(image_path, "rb") as f:
    image_bytes = f.read()

messages = [
    HumanMessage(
        content=[
            {
                "type": "image",
                "image": {
                    "format": "jpeg",
                    "source": {
                        "bytes": image_bytes
                    }
                }
            },
            "What is this image about?"
        ]
    )
]

llm.invoke(messages)

Document sample code

from langchain_core.messages import HumanMessage
from langchain_aws import ChatBedrock

llm = ChatBedrock(
    model_id="anthropic.claude-3-sonnet-20240229-v1:0",
    beta_use_converse_api=True
)

# Convert document to bytes
doc_path = "documents/random-doc.pdf"
doc_bytes = None
with open(doc_path, "rb") as f:
    doc_bytes = f.read()

messages = [
    HumanMessage(
        content=[
            {
                "type": "document",
                "document": {
                    "format": "pdf",
                    "name": "random-doc",
                    "source": {
                        "bytes": doc_bytes
                    }
                }
            },
            "What is this document about?"
        ]
    )
]

llm.invoke(messages)

Related to #75
Fixes #132

[baskaryan]

could we add/update unit test for this?

[3coins]

Thanks for calling this out. Looks like, both image and document are not supported in the output at the moment, so we should remove both.
https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_Message.html

Let me know if I am missing anything.

[3coins]

@baskaryan
Added unit tests.