fix(postgres): accept full_page_writes off on Amazon Aurora PostgreSQL only

Generation qualification refused every Amazon Aurora PostgreSQL server:
Aurora always reports full_page_writes = off and has no parameter to change
it, because its storage layer does not write torn pages.

The settings query now also returns
to_regprocedure('aurora_version()') IS NOT NULL (true on Aurora, false on
stock PostgreSQL, never an error). full_page_writes = off is accepted only
when that is true. Stock PostgreSQL must still report it on, and fsync on,
synchronous_commit on or remote_apply and every other check are unchanged
on both. The refusal text now says full-page writes are not required on
Aurora.

Tests run on a real postgres:17 engine whose settings are really changed;
only Aurora is simulated, by creating a function named aurora_version() in
the test database.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

foundation/src/test/java/com/kingsrook/qbits/documentgeneration/PostgresGenerationDatabase.java

@@ -52,13 +52,24 @@ final class PostgresGenerationDatabase implements AutoCloseable
     ** Starts only this suite's loopback container with durable settings.
     ***************************************************************************/
    PostgresGenerationDatabase()
+   {
+      this(true);
+   }
+
+   /***************************************************************************
+    ** Pinned durability settings come from the server command line, which no
+    ** ALTER SYSTEM can override. An unpinned engine starts with the same values
+    ** (the PostgreSQL defaults) and lets a test weaken them through system().
+    ***************************************************************************/
+   PostgresGenerationDatabase(boolean pinned)
    {
       // pgjdbc announces the JVM zone as the session TimeZone; qualification requires UTC.
       previousZone = java.util.TimeZone.getDefault();
       java.util.TimeZone.setDefault(java.util.TimeZone.getTimeZone("UTC"));
       container = new GenericContainer<>(IMAGE)
          .withEnv("POSTGRES_PASSWORD", rootPassword).withEnv("POSTGRES_DB", "bootstrap")
-         .withCommand("postgres", "-c", "fsync=on", "-c", "synchronous_commit=on", "-c", "full_page_writes=on", "-c", "max_connections=60")
+         .withCommand(pinned ? new String[] { "postgres", "-c", "fsync=on", "-c", "synchronous_commit=on", "-c", "full_page_writes=on", "-c", "max_connections=60" }
+            : new String[] { "postgres", "-c", "max_connections=60" })
          .withExposedPorts(5432)
          .withCreateContainerCmdModifier(command -> command.getHostConfig().withMemory(768L * 1024 * 1024).withNanoCPUs(2_000_000_000L)
             .withPortBindings(FixtureEndpoint.publishedBinding(5432)))
@@ -143,6 +154,38 @@ final class PostgresGenerationDatabase implements AutoCloseable
       }
    }
 
+   /***************************************************************************
+    ** Change one reloadable server setting of an unpinned engine (ALTER SYSTEM and
+    ** a configuration reload), then wait until a new session actually reports it.
+    ** Fixed fixture names and values only, never application input.
+    ***************************************************************************/
+   void system(String name, String value) throws Exception
+   {
+      ConnectionManager.closeConnectionProviders();
+      try(var connection = DriverManager.getConnection(server + "bootstrap" + OPTIONS, "postgres", rootPassword); var statement = connection.createStatement())
+      {
+         statement.execute("ALTER SYSTEM SET " + name + " = '" + value + "'");
+         statement.execute("SELECT pg_reload_conf()");
+      }
+      long deadline = System.nanoTime() + java.time.Duration.ofSeconds(30).toNanos();
+      while(true)
+      {
+         try(var connection = DriverManager.getConnection(server + "bootstrap" + OPTIONS, "postgres", rootPassword); var statement = connection.createStatement();
+            var row = statement.executeQuery("SELECT current_setting('" + name + "')"))
+         {
+            if(row.next() && value.equals(row.getString(1)))
+            {
+               return;
+            }
+         }
+         if(System.nanoTime() >= deadline)
+         {
+            throw new IllegalStateException("PostgreSQL fixture did not apply " + name);
+         }
+         Thread.sleep(100);
+      }
+   }
+
    /***************************************************************************
     ** Cold server restart retains only this container's data layer (committed
     ** data must survive; Docker may publish a different loopback port).