iso-image: make sure volumeID is less than 32 chars

nixos/modules/installer/cd-dvd/iso-image.nix

@@ -524,6 +524,19 @@ in
   };
 
   config = {
+    assertions = [
+      {
+        assertion = !(stringLength config.isoImage.volumeID > 32);
+        # https://wiki.osdev.org/ISO_9660#The_Primary_Volume_Descriptor
+        # Volume Identifier can only be 32 bytes
+        message = let
+          length = stringLength config.isoImage.volumeID;
+          howmany = toString length;
+          toomany = toString (length - 32);
+        in
+        "isoImage.volumeID ${config.isoImage.volumeID} is ${howmany} characters. That is ${toomany} characters longer than the limit of 32.";
+      }
+    ];
 
     boot.loader.grub.version = 2;