solanum: fix MOTD

Previously this defaulted to the default MOTD in the solanum source
tree, and I don't want my friends to laugh at me. Includes a patch to
the tests to ensure that the MOTD is actually set.

This replicates the fix done in #109705 (solanum is a fork of charybdis,
so they share fundamental logic for this).

Signed-off-by: Christine Dodrill <[e-mail]>

nixos/tests/solanum.nix

···
       networking.firewall.allowedTCPPorts = [ ircPort ];
       services.solanum = {
         enable = true;
+        motd = ''
+          The default MOTD doesn't contain the word "nixos" in it.
+          This one does.
+        '';
       };
     };
   } // lib.listToAttrs (builtins.map (client: lib.nameValuePair client {
···
           ${client}.systemctl("start ii")
           ${client}.wait_for_unit("ii")
           ${client}.wait_for_file("${iiDir}/${server}/out")
+        ''
+        # look for the custom text in the MOTD.
+        ''
+          ${client}.wait_until_succeeds("grep 'nixos' ${iiDir}/${server}/out")
         ''
         # wait until first PING from server arrives before joining,
         # so we don't try it too early

pkgs/servers/irc/solanum/default.nix

···
     ./dont-create-logdir.patch
   ];
 
+  postPatch = ''
+    substituteInPlace include/defaults.h --replace 'ETCPATH "' '"/etc/solanum'
+  '';
+
   configureFlags = [
     "--enable-epoll"
     "--enable-ipv6"