The overlay has been removed and the package financier-dist is now
always built with the Nixpkgs version from our flake inputs. Overlays
can be applied to any version of Nixpkgs, but our package does not work
with all versions of Nixpkgs.
For example, we currently built our package with Node 12. The
nodejs-12_x has been marked as insecure on the
21.05 branch in May 2022 breaking our build and consequently our module
and all configurations that rely on it.
Usually, it would be very bad to pin to an old Nixpkgs version as we miss
potential security updates. But we build a static website and it is very
unlikely that it has any security issues.