Exceeding SQS message size limit when attaching image via a customized bot published API

## Describe the bug

When I call an API published with an image encoded to base64, the API returns 500 error with following detail:
```
'detail': 'An error occurred (InvalidParameterValue) when '
'calling the SendMessage operation: One or more '
'parameters are invalid. Reason: Message must be '
'shorter than 262144 bytes.'
```
This is due to a hard limit of SQS message size ([document](https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/quotas-messages.html))

## To Reproduce

1. publish customized API
2. run following code

```python
import base64
import json
import requests
from pprint import pprint

base_url = ""

headers = {
"Content-Type": "application/json",
"x-api-key": ""
}

input_data = "describe what is in the image"
image_path = "" #image size to be >~200KB

def start_conversation(model, message, image_files):
url = f"{base_url}/conversation"
content = [
{
"contentType": "text",
"body": message
}
]

for image_file in image_files:
with open(image_file, "rb") as f:
image_data = f.read()
image_base64 = base64.b64encode(image_data).decode('utf-8')
content.append({
"contentType": "image",
"mediaType": "image/png", #or other appropriate MIME type
"body": image_base64
})

payload = {
"message": {
"content": content,
"model": model
}
}
response = requests.post(url, data=json.dumps(payload), headers=headers)
if response.status_code == 200:
data = response.json()
return data
else:
return {"status": f"Failed to start conversation with status code {response.status_code}", "response":response.json()}

conversation_start_result = start_conversation("claude-v3-sonnet", input_data, [image_path])
pprint(conversation_start_result)
```

## Screenshots
N/A

## Additional context
N/A

Start by reproducing the published API request at the conversation endpoint with an image larger than approximately 200 KB, and trace where the request reaches Amazon SQS. Confirm the 262144-byte message limit and identify the API path responsible; done means image requests no longer fail with the reported SQS size error.

Written by the indexing model from the issue text.