Support CORS for openai api server

[aisensiy]

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Motivation

Support CORS for openai api.

Modification

Add CORS headers.

BC-breaking (Optional)

Use cases (Optional)

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit tests to ensure the correctness.
3. If the modification has a dependency on downstream projects of a newer version, this PR should be tested with all supported versions of downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[lvhan028]

@aisensiy could you please explain more about the motivation?
I

[aisensiy]

CORS (Cross-Origin Resource Sharing) is a security mechanism implemented by web browsers to protect users from unauthorized access to their data. It allows web pages running on different domains to interact with each other. By adding CORS support, it enables this api to respond to requests from other domains.

For example this project running on http://localhost:8080 and an other web application running on http://localhost:3000. Calling this openai api from http://localhost:3000 will show an error message without the CORS configuration.

Access to XMLHttpRequest at 'http://localhost:8080/v1/chat/completions' from origin 'http://localhost:3000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

[lvhan028]

Shouldn't the server who is listening to 3000 port deal with it?

[aisensiy]

No, the api provider should handle it. The api provider provide the CORS headers to tell others which origin can access the api.

cors-error.mp4

Please read more information about this in https://fastapi.tiangolo.com/tutorial/cors/

[aisensiy]

@AllentDan @lvhan028 So there is still some concerns about this PR?

[AllentDan]

Can we make it an option just like FastChat?
Maybe we can provide more args to launch api_server.

[tpoisonooo]

@aisensiy Excellent, please make it as an option, enable CORS by default.

[tpoisonooo]

make it optional, enable CORS by default.

[AllentDan]

LGTM