Use x-forwarded-host header to determine the root url, and let users provide a full root_path to override the automatically determined root url

[abidlabs]

This PR fixes the issue that we're seeing where Gradio apps don't render properly on k8 environments and some other places where the URL of the Gradio app is behind an app router or proxy.

The fix is to look at the x-forwarded-host header, if available, and use that in place of the request URL, as this header points to the public URL of the Gradio app.

In addition, we provide users with a fallback in case Gradio is not able to determine the root url automatically. By providing a full root_path (either as an env variable or as a parameter in launch()), users can set their own root url, which takes precedence over the one Gradio constructs automatically.

Closes: #7317

[gradio-pr-bot]

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Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/3f6ced361dfac11fe1545fb16ae643f1e93e0af1/gradio-4.20.1-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@3f6ced361dfac11fe1545fb16ae643f1e93e0af1#subdirectory=client/python"

[gradio-pr-bot]

🦄 change detected

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gradio	patch

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Use x-forwarded-host header to determine the root url, and let users provide a full root_path to override the automatically determined root url

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[freddyaboulton]

Nice fix @abidlabs !

[abidlabs]

Thanks a bunch for the review @freddyaboulton