Support OpenAI OSS Models through Bedrock

Bedrock supported OpenAI OSS weighted models in August 2025, these models are already pulled into the chatbot models but we need to add additional implementation to process OpenAI specification in request and responses.

https://docs.aws.amazon.com/bedrock/latest/userguide/model-parameters-openai.html
https://aws.amazon.com/blogs/aws/openai-open-weight-models-now-available-on-aws/