* Refactor AWS adapter to improve model management
- Replace hardcoded model list in `adapter.go` with a function to get models from `awsModelIDMap`
- Update `GetModelList` function to return model list directly
- Add `GetChannelName` function to get channel name from `Adaptor` object
* Improve error handling and code organization in main.go
- Replace switch statement with a map to map AWS model IDs to OpenAI model IDs
- Return an error if the model is not found in the map
- Use a single return statement instead of wrapping multiple return statements in the `awsModelID` function
- Add a new error message for when the model is not found in the map in the `Handler` function
