nixos/postgresql: move postStart into separate unit

This avoids restarting the postgresql server, when only ensureDatabases
or ensureUsers have been changed. It will also allow to properly wait
for recovery to finish later.

To wait for "postgresql is ready" in other services, we now provide a
postgresql.target.

Resolves #400018

Co-authored-by: Marcel <me@m4rc3l.de>

nixos/tests/postgresql/anonymizer.nix

@@ -28,7 +28,7 @@ let
       testScript = ''
         start_all()
         machine.wait_for_unit("multi-user.target")
-        machine.wait_for_unit("postgresql.service")
+        machine.wait_for_unit("postgresql.target")
 
         with subtest("Setup"):
             machine.succeed("sudo -u postgres psql --command 'create database demo'")

nixos/tests/postgresql/pgjwt.nix

@@ -40,7 +40,7 @@ let
         in
         ''
           start_all()
-          master.wait_for_unit("postgresql")
+          master.wait_for_unit("postgresql.target")
           master.succeed(
               "${pkgs.sudo}/bin/sudo -u ${sqlSU} ${pgProve}/bin/pg_prove -d postgres -v -f ${pgjwt.src}/test.sql"
           )

nixos/tests/postgresql/postgresql-jit.nix

@@ -29,7 +29,7 @@ let
 
       testScript = ''
         machine.start()
-        machine.wait_for_unit("postgresql.service")
+        machine.wait_for_unit("postgresql.target")
 
         with subtest("JIT is enabled"):
             machine.succeed("sudo -u postgres psql <<<'show jit;' | grep 'on'")

nixos/tests/postgresql/postgresql-wal-receiver.nix

@@ -62,7 +62,7 @@ let
 
       testScript = ''
         # make an initial base backup
-        machine.wait_for_unit("postgresql")
+        machine.wait_for_unit("postgresql.target")
         machine.wait_for_unit("postgresql-wal-receiver-main")
         # WAL receiver healthchecks PG every 5 seconds, so let's be sure they have connected each other
         # required only for 9.4
@@ -99,7 +99,7 @@ let
         machine.systemctl("start postgresql")
         machine.wait_for_file("${postgresqlDataDir}/recovery.done")
         machine.systemctl("restart postgresql")
-        machine.wait_for_unit("postgresql")
+        machine.wait_for_unit("postgresql.target")
 
         # check that our records have been restored
         machine.succeed(

nixos/tests/postgresql/postgresql.nix

@@ -82,7 +82,7 @@ let
 
 
           machine.start()
-          machine.wait_for_unit("postgresql")
+          machine.wait_for_unit("postgresql.target")
 
           with subtest("Postgresql is available just after unit start"):
               machine.succeed(
@@ -94,7 +94,7 @@ let
               import time
               time.sleep(2)
               machine.start()
-              machine.wait_for_unit("postgresql")
+              machine.wait_for_unit("postgresql.target")
 
           machine.fail(check_count("SELECT * FROM sth;", 3))
           machine.succeed(check_count("SELECT * FROM sth;", 5))
@@ -219,7 +219,7 @@ let
         ''
           import json
           machine.start()
-          machine.wait_for_unit("postgresql")
+          machine.wait_for_unit("postgresql.target")
 
           with subtest("All user permissions are set according to the ensureClauses attr"):
               clauses = json.loads(

nixos/tests/postgresql/wal2json.nix

@@ -27,7 +27,7 @@ let
       };
 
       testScript = ''
-        machine.wait_for_unit("postgresql")
+        machine.wait_for_unit("postgresql.target")
         machine.succeed(
             "sudo -u postgres psql -qAt -f ${./wal2json/example2.sql} postgres > /tmp/example2.out"
         )