[Feature Request]I want Amazon Kendra to support GenAI

## Describe the solution you'd like

I would like it to support Amazon Kendra GenAI.

## Why the solution needed

Amazon Kendra GenAI enables you to build highly accurate and scalable RAGs.
RAGs with advanced analysis options have strict limitations on the number of files and total size, making them difficult to put into practical use, but Amazon Kendra GenAI makes it easy to put into practical use.

## Additional context

I tried to use it with external knowledge, but the following error occurred and it could not be used.


## Implementation feasibility

Are you willing to collaborate with us to discuss the solution, decide on the approach, and assist with the implementation?

- [ ] Yes, I am able to implement the feature and create a pull request.
- [X] No, I am unable to implement the feature, but I am open to discussing the solution.

Start by locating the existing external knowledge integration and reviewing how Amazon Kendra is currently handled. The issue names no files or tests; done would mean supporting Amazon Kendra GenAI without the reported error and verifying the integration works.

Written by the indexing model from the issue text.