nixos/public-inbox: correctly merge config

This needs to be defined as an attribute set two layers deep so that
multiple settings in the same namespace, declared in two different
modules, will be merged together.

For example, the following previously wouldn't be merged properly:

    { ... }:

    {
      imports = [ (
        { ... }: {
          services.public-inbox.config.publicinbox.listid = "foo.example.com;
        }
      ) ];

      services.public-inbox.config.publicinbox.css =
        "https://example.com/pi.css";
    }

1 files changed, 1 insertions, 1 deletions

diff --git a/nixpkgs/nixos/modules/services/mail/public-inbox.nix b/nixpkgs/nixos/modules/services/mail/public-inbox.nix
index f6c08bf2e45b..d503f5aa2ef6 100644
--- a/nixpkgs/nixos/modules/services/mail/public-inbox.nix
+++ b/nixpkgs/nixos/modules/services/mail/public-inbox.nix
@@ -318,7 +318,7 @@ in
       };
 
       config = mkOption {
-        type = types.attrs;
+        type = with types; attrsOf attrs;
         default = {};
         description = ''
           Additional structured config for the public-inbox config file