nixos/hydra: remove hydra-migration upgrade path

This should NOT be backported to 20.09!

When 21.03 is released, the DB changes are about a year old and
operators had two release cycles for the upgrade. At this point it
should be fair to remove the compat layer to reduce the complexity of
the module itself.

nixos/tests/hydra/db-migration.nix

@@ -1,92 +0,0 @@
-{ system ? builtins.currentSystem
-, pkgs ? import ../../.. { inherit system; }
-, ...
-}:
-
-let inherit (import ./common.nix { inherit system; }) baseConfig; in
-
-with import ../../lib/testing-python.nix { inherit system pkgs; };
-with pkgs.lib;
-
-{ mig = makeTest {
-    name = "hydra-db-migration";
-    meta = with pkgs.stdenv.lib.maintainers; {
-      maintainers = [ ma27 ];
-    };
-
-    nodes = {
-      original = { pkgs, lib, ... }: {
-        imports = [ baseConfig ];
-
-        # An older version of Hydra before the db change
-        # for testing purposes.
-        services.hydra.package = pkgs.hydra-migration.overrideAttrs (old: {
-          inherit (old) pname;
-          version = "2020-02-06";
-          src = pkgs.fetchFromGitHub {
-            owner = "NixOS";
-            repo = "hydra";
-            rev = "2b4f14963b16b21ebfcd6b6bfa7832842e9b2afc";
-            sha256 = "16q0cffcsfx5pqd91n9k19850c1nbh4vvbd9h8yi64ihn7v8bick";
-          };
-        });
-      };
-
-      migration_phase1 = { pkgs, lib, ... }: {
-        imports = [ baseConfig ];
-        services.hydra.package = pkgs.hydra-migration;
-      };
-
-      finished = { pkgs, lib, ... }: {
-        imports = [ baseConfig ];
-        services.hydra.package = pkgs.hydra-unstable;
-      };
-    };
-
-    testScript = { nodes, ... }: let
-      next = nodes.migration_phase1.config.system.build.toplevel;
-      finished = nodes.finished.config.system.build.toplevel;
-    in ''
-      original.start()
-      original.wait_for_unit("multi-user.target")
-      original.wait_for_unit("postgresql.service")
-      original.wait_for_unit("hydra-init.service")
-      original.require_unit_state("hydra-queue-runner.service")
-      original.require_unit_state("hydra-evaluator.service")
-      original.require_unit_state("hydra-notify.service")
-      original.succeed("hydra-create-user admin --role admin --password admin")
-      original.wait_for_open_port(3000)
-      original.succeed("create-trivial-project.sh")
-      original.wait_until_succeeds(
-          'curl -L -s http://localhost:3000/build/1 -H "Accept: application/json" |  jq .buildstatus | xargs test 0 -eq'
-      )
-
-      out = original.succeed("su -l postgres -c 'psql -d hydra <<< \"\\d+ builds\" -A'")
-      assert "jobset_id" not in out
-
-      original.succeed(
-          "${next}/bin/switch-to-configuration test >&2"
-      )
-      original.wait_for_unit("hydra-init.service")
-
-      out = original.succeed("su -l postgres -c 'psql -d hydra <<< \"\\d+ builds\" -A'")
-      assert "jobset_id|integer|||" in out
-
-      original.succeed("hydra-backfill-ids")
-
-      original.succeed(
-          "${finished}/bin/switch-to-configuration test >&2"
-      )
-      original.wait_for_unit("hydra-init.service")
-
-      out = original.succeed("su -l postgres -c 'psql -d hydra <<< \"\\d+ builds\" -A'")
-      assert "jobset_id|integer||not null|" in out
-
-      original.wait_until_succeeds(
-          'curl -L -s http://localhost:3000/build/1 -H "Accept: application/json" |  jq .buildstatus | xargs test 0 -eq'
-      )
-
-      original.shutdown()
-    '';
-  };
-}

nixos/tests/hydra/default.nix

@@ -11,7 +11,7 @@ let
   inherit (import ./common.nix { inherit system; }) baseConfig;
 
   hydraPkgs = {
-    inherit (pkgs) hydra-migration hydra-unstable;
+    inherit (pkgs) hydra-unstable;
   };
 
   makeHydraTest = with pkgs.lib; name: package: makeTest {