Allow overriding URL for staging OpenAPI resources

We use an OpenAPI resource for our retools apps. Our openapi spec has our production endpoints listed as "server" in it.

Retool seems to pick that value up automatically - however this has the downside where there is currently no way to only override this value when creating the staging version of that resource - you need to point to two different files. This means that every time our spec changes, we need to create a second copy of it for staging, and upload both files.

It would be awesome if we could point to a single file, and override the base URL it should use for staging in the retool UI..