Refactor models.rs

[mdevino]

Description

As an orchestrator developer, I'd like to have an easier time when navigating through the code, so that I can develop faster.

Discussion

The models.rs file holds a lot of structs related to HTTP requests and responses. As we develop new endpoints, this file is only going to grow in size.

The code would be easier to navigate if we split these structs into different files. One option would be to split in files by endpoint. For example, the structs related to /api/v2/text/generation-detection are GenerationWithDetectionHttpRequest and GuardrailsTextGenerationParameters for the request, and GenerationWithDetectionResult and DetectionResult for the response. We could have these into a separate file. We would probably also need a file for structs used across multiple endpoints, such as GuardrailsTextGenerationParameters and DetectionResult.

I'm not entirely sure the suggestion above is the best approach, but I'm opening this issue so that we can kickstart the discussion.

Acceptance Criteria

• Unit tests cover new/changed code