Locally index a package.txt hoogle file after generating

Hey there! My question is whether it's possible to either:

• generate hoogle via packages in ghc-pkg and some other package not in there
• on a running local hoogle, index an additional package that's not in it.

My situation is that we would like a local hoogle with project dependencies docs but also the project's docs themselves. We use nix for dependencies, so that once in the shell, docs are available via ghc-pkg for all the dependencies, but not the project itself. I can fairly easily generate the docs for the project itself via cabal new-haddock --haddock--hoogle, but I'm not sure how to get that file into the hoogle database once it's made. If http://hackage.haskell.org/api is also the API for a local hoogle db it seem likes some variation of curl -XPOST localhost:8080/packages -H 'Accept: text/plain' -F package=@/path/to/file should work but nothing I've tried makes it accept it (usually it returns "File not found"). Is there a way to do something like this?

Start by reproducing the local setup with ghc-pkg, cabal new-haddock --haddock--hoogle, and the attempted POST to localhost:8080/packages. Trace how a local Hoogle database is built and how that endpoint handles package files; done means a generated project package.txt can be indexed alongside dependency documentation.