* FS-51 Report unavailable clients for Proteus messages

Changing the return types to match the ticket.
Adding tests and fixing some logic errors.

* testing changes. Reworking how failing federators are tested.

Rewriting the test, basing it off an existing test that is almost what
is needed, and removing the prior test.

* FS-51: Adding changes from PR review and more tests

* Updating tests

* FS-51: Moving unit tests to a better module

* FS-51: Formatting and linters

* FS-51: Updating nix with generate-local-nix-packages.sh

* FS-51: Fixing an error