nixos/kubernetes: add extraConfig to kubelet config (#338526)

nixos/doc/manual/release-notes/rl-2411.section.md

@@ -454,6 +454,8 @@
 
 - Kanidm previously had an incorrect systemd service type, causing dependent units with an `after` and `requires` directive to start before `kanidm*` finished startup. The module has now been updated in line with upstream recommendations.
 
+- The kubelet configuration file can now be amended with arbitrary additional content using the `services.kubernetes.kubelet.extraConfig` option.
+
 - To facilitate dependency injection, the `imgui` package now builds a static archive using vcpkg' CMake rules.
   The derivation now installs "impl" headers selectively instead of by a wildcard.
   Use `imgui.src` if you just want to access the unpacked sources.

nixos/modules/services/cluster/kubernetes/kubelet.nix

@@ -66,6 +66,7 @@ let
     // lib.optionalAttrs (cfg.clusterDomain != "")  { clusterDomain = cfg.clusterDomain; }
     // lib.optionalAttrs (cfg.clusterDns != [])     { clusterDNS = cfg.clusterDns; }
     // lib.optionalAttrs (cfg.featureGates != {})   { featureGates = cfg.featureGates; }
+    // lib.optionalAttrs (cfg.extraConfig != {})    cfg.extraConfig
   ));
 
   manifestPath = "kubernetes/manifests";
@@ -184,6 +185,12 @@ in
       type = separatedString " ";
     };
 
+    extraConfig = mkOption {
+      description = "Kubernetes kubelet extra configuration file entries.";
+      default = {};
+      type = attrsOf attrs;
+    };
+
     featureGates = mkOption {
       description = "Attribute set of feature gate";
       default = top.featureGates;