Add a comment about merging modules and base.nix.

morph/lib/base.nix

+# This module contains settings and configuration that apply to all nodes in a grid.
 { lib, config, ...}:
 {
   options.grid = {

morph/lib/issuer.nix

-# This is all of the static NixOS system configuration necessary to specify an
-# "issuer"-type system.  The configuration has various holes in it which must
-# be filled somehow.  These holes correspond to configuration which is not
-# statically known.  This value is suitable for use as a module to be imported
-# into a more complete system configuration.  It is expected that the holes
-# will be filled by a sibling module created by ``customize-issuer.nix``.
+# This, along with `customize-issuer.nix, contains all of the NixOS system
+# configuration necessary to specify an "issuer"-type system.  Originally, this
+# file has all the static configuration, and `customize-issuer.nix` was a function
+# that filled in the holes. We are in the process of merging the modules, using settings
+# instead of function arguments.
+# See https://whetstone.privatestorage.io/privatestorage/PrivateStorageio/-/issues/80
 { config, ...}:
 let
   inherit (config.grid) publicKeyPath privateKeyPath;