Fail to import pipewire metadata.h when building package

I am attempting to package discord-screenaudio, but the build is currently failing with:

/build/source/submodules/rohrkabel/src/metadata.cpp:7:10: fatal error: pipewire/extensions/metadata.h: No such file or directory
    7 | #include <pipewire/extensions/metadata.h>
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Pipewire is in the buildInputs and as far as I can tell, other projects using the same file import it with no issues. I would greatly appreciate any help, I’m not very familiar with cmake, but would like to get this working.

Here is my PR draft and here is the default.nix file.