Znix already did something about it: https://gitlab.com/znixian/payday2-shader-tool
So we need some way to explode it into individual pieces, implode them back together, and overwrite a single entry in the database.
It looks like it's GLSL in there for the OpenGL ones, and HLSL bytecode for the D3D ones. We may also need to consult the render template list. It's also the same container as model files, so a little bit can be reused, at least.