Set root correctly for Gradio apps that are deployed behind reverse proxies

[abidlabs]

This PR fixes the issues that we're seeing around the root url when Gradio apps are deployed behind nginx or other reverse proxies. As far as I can tell, there were two separate issues:

1. The root_path parameter in Blocks was being ignored. This parameter is needed to tell Gradio (FastAPI really) the subpath where the Gradio app is being served from. E.g. if you are serving Gradio on www.mydomain.com/demo, it should be /demo. Now, its correctly accounted for. While its hard to write an end-to-end test for this, I have added unit tests for get_root_url() and I have tested it by running an nginx reverse proxy on an ec2 instance here: http://35.85.61.147/gradio-demo/

Main:

This PR:

2. When serving behind an nginx proxy, the "x-forwarded-proto" is supposed to designate whether the original website is being served on https or on http. We use this to set http/https in the root in the config. However, sometimes this header is not set correctly, or it fails to contain the protocol information. This causes a problem on websites that are using https because we try to fetch certain gradio static assets on http, which browsers automatically block. I added another check in the frontend to check to see if current window is being served with https and if so, upgrade the config.root to be https as well

Closes: #7391 (as confirmed by @pseudotensor)
Closes: #7317

(May close?) #6920

[gradio-pr-bot]

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Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/335daba3999f0c478ae2d62cfa051be8a170476d/gradio-4.18.0-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@335daba3999f0c478ae2d62cfa051be8a170476d#subdirectory=client/python"

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@gradio/client	patch
gradio	patch

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Set root correctly for Gradio apps that are deployed behind reverse proxies

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[freddyaboulton]

Nice fix @abidlabs !

[abidlabs]

Thanks @freddyaboulton for the review! I'll clean this up tomorrow and merge it in.

cc @pngwn and @aliabid94 as well if y'all wanna take a look at this before that