OpenAPI: handle "servers"

[alukach]

If an upstream API is using root_path on FastAPI¹ (e.g. if serving behind an API Gateway which requires a stage in the path), then the OpenAPI spec likely includes a servers declaration². That declaration should be removed when augmenting the OpenAPI spec.

Additionally, if the proxy API is using a root_path, then we should ensure that the serves declaration appropriately demonstrates that.

Footnotes

1. https://fastapi.tiangolo.com/advanced/behind-a-proxy/ ↩

2. https://swagger.io/docs/specification/v3_0/api-host-and-base-path/ ↩