Allow for message history to be omitted when making request to llm

[DarioPanada]

Feature: Add support for appending messages to existing conversations while providing the option to include only the latest message in the conversation history.

Change: Introduces an optional boolean flag, exclude_history. When set to true, only the most recent message in the conversation is passed instead of the complete history.

Benefits:

1. Reduced Payload Size: Enables compliance with services that have payload size limits (e.g., AWS CloudFront).
2. Optimized Performance: Can potentially improve request processing speed and efficiency by reducing data transmission overhead.
3. Developer Flexibility: Offers developers the choice to manage conversation history as needed in their backend systems.

Use Case

In scenarios where back-end services impose payload size restrictions, this flag allows developers to selectively exclude potentially large conversation histories. A typical use case is sending inference requests containing only the latest user prompt, while managing a more extensive conversation history in the backend.

Important Note: Developers will still need to implement their own backend persistence mechanisms if they require LLM access to the complete conversation history beyond the latest user message.