bug#42173: [PATCH 2/2] services: nix: Fix sandbox.

Hi! Oleg Pykhalov skribis: > * gnu/tests/package-management.scm: New file. > * gnu/local.mk: Add this. > * gnu/services/nix.scm (): New record. > (nix-activation): Generate Nix config file. > (nix-service-type): Add default value. > (nix-shepherd-service): Allow provide Nix package. > * doc/guix

bug#42173: [PATCH 2/2] services: nix: Fix sandbox.

* gnu/tests/package-management.scm: New file. * gnu/local.mk: Add this. * gnu/services/nix.scm (): New record. (nix-activation): Generate Nix config file. (nix-service-type): Add default value. (nix-shepherd-service): Allow provide Nix package. * doc/guix.texi (Miscellaneous Services)[Nix service]: