API swagger docs inaccessible behind proxy

Going to the docs page sends you to this error

I've seen this before and the solution was to set the `--root-path` flag as described here: https://fastapi.tiangolo.com/advanced/behind-a-proxy/#proxy-with-a-stripped-path-prefix

The issue does not name a file or test. Start by reproducing the Swagger docs failure when the application is served behind a proxy, then read FastAPI's linked 'behind a proxy' guidance and inspect the application's startup entry point for the `--root-path` setting. Done means the docs page loads successfully through the proxy without the shown error.

Written by the indexing model from the issue text.