[Feature] - Set remote SD URL with environment variable

[sphuff]

Motivation:
Allows users to use a remote instance of the Automatic UI

How to use:

export SD_URL=http://104.143.3.146:10758 (example URL I was using)
// start app
uvicorn serverMain:app --reload

Or you can do the following:

• Add set SD_URL=http://104.143.3.146:10758 in your start_server.bat

How it works:
All requests are proxied through the local python server. The remote SD server is then hit

[sphuff]

still defaults to the local instance on 7860

[WadeWarren]

This is great – thanks!

[AbdullahAlfaraj]

this is awesome.
all of the generation related request like (img2img, inpaint) are working
but the progressbar seem to be broken. it's stuck at 0%.
I will keep testing it.

[sphuff]

@AbdullahAlfaraj ah I see what's happening - the server is only handling one request at a time, so the progress request isn't resolving until after the images are done. I should be able to do the image task in the background to fix - will update shortly

[sphuff]

Ok, done. I ending up adding asyncio and httpx to handle the async requests on the python side. So now I'm seeing it working with the progress request, as well as the txt2img/img2img

[AbdullahAlfaraj]

@sphuff fantastic work.