AzureOpenAI misc fixes

[chip-davis]

Hello! This PR is by no means production ready, I mainly wanted to alert you to a couple issues I had with Azure and my (super quick) fixes.

Changes made:

• The upload.py file was always creating a PGVector store with OpenAIEmbeddings(). In my use case, I am only using Azure. So without an openai key set, the app would not start up. I created a simple function that sees if there is an openai key env variable set and returns a PGVector store with OpenAIEmbeddings. If that was not found, it tries the same with Azure. If that was not found, it raises an exception.
• In llms.py the AzureChatOpenAI was created with the openai_api_base variable set. As of openai>=1.0.0 this has been changed to azure_endpoint.
• Also in llms.py during the startup of the app, it would crash due to me not having an OpenAI api key set. I created a simple try / catch block to try and fall back to Azure in that instance.

These changes work for me but as I do not have an openai api key I can not test for conflicts caused by these changes.

[mkorpela]

@chip-davis thanks for the contribution! Azure is an important thing to make work.

[chip-davis]

@chip-davis thanks for the contribution! Azure is an important thing to make work.

Sure thing! Thanks for merging :)