Improved API key validation on ChatGPT integration

The ChatGPT app has been improved in several ways. We have added a Test button on the app to allow for testing the inputted OpenAI API key:

Furthermore, we have improved potential errors being returned from the OpenAI API when clicking the Get suggestion button in the search UI. Rather than failing silent, the UI will now indicate if the API key is wrong, the usage limit has been reached, and more errors.

These changes make it easier than ever to integrate AI-suggested error resolution directly on your errors in elmah.io.