refactor: generalize flake input injection

deploy/rpi5/default.nix

@@ -1,9 +1,11 @@
 { config, lib, ... }:
 {
   options.aether.deploy.rpi5 = {
-    kernelPackages = lib.mkOption {
+    _internal.kernelPackages = lib.mkOption {
       type = lib.types.raw;
-      description = "Kernel package to use for Raspberry Pi 5 support";
+      description = ''
+        Kernel package to use for Raspberry Pi 5 support.
+      '';
     };
   };
 
@@ -11,7 +13,7 @@
     let cfg = config.aether.deploy.rpi5;
     in {
       nixpkgs.system = "aarch64-linux";
-      boot.kernelPackages = cfg.kernelPackages;
+      boot.kernelPackages = cfg._internal.kernelPackages;
       boot.loader.systemd-boot.enable = true;
       boot.loader.efi.canTouchEfiVariables = false;
     };

flake.nix

@@ -19,23 +19,43 @@ outputs = inputs@{ self, nixpkgs, agenix, rpi5-kernel, ... }:
   let
     inherit (nixpkgs) lib;
 
+    # Extra config applied to each module
+    # (Mostly used for injecting flake inputs)
+    extraConfig = {
+      deploy-rpi5 = {
+        aether.deploy.rpi5._internal.kernelPackages = lib.mkDefault
+          rpi5-kernel.legacyPackages.aarch64-linux.linuxPackages_rpi5;
+      };
+    };
+
     moduleNames =
       let sub = builtins.readDir ./modules;
       in builtins.filter
         (d: sub.${d} == "directory")
         (builtins.attrNames sub);
 
-    modules = lib.genAttrs moduleNames (name: ./modules/${name});
+    deployNames =
+      let sub = builtins.readDir ./deploy;
+      in builtins.map (d: "deploy-${d}")
+        (builtins.filter
+          (d: sub.${d} == "directory")
+          (builtins.attrNames sub));
+
+    modules = lib.genAttrs moduleNames
+      (name: ./modules/${name});
+    deployments = lib.genAttrs deployNames
+      (name: ./deploy/${lib.removePrefix "deploy-" name});
+
+    modulesWithCfg = builtins.mapAttrs (k: v: {
+      imports = [ v ];
+    } // extraConfig.${k} or {}) modules;
+    deploymentsWithCfg = builtins.mapAttrs (k: v: {
+      imports = [ v ];
+    } // extraConfig.${k} or {}) deployments;
   in {
     nixosModules =
-      modules
-      // {
-        all.imports = lib.attrValues modules;
-        deploy-rpi5 = { lib, ... }: {
-          imports = [ ./deploy/rpi5 ];
-          aether.deploy.rpi5.kernelPackages = lib.mkDefault
-            rpi5-kernel.legacyPackages.aarch64-linux.linuxPackages_rpi5;
-        };
+      modulesWithCfg // deploymentsWithCfg // {
+        all.imports = lib.attrValues modulesWithCfg;
       };
 
     nixosConfigurations."toki-aether" =