API(clanInternals): add 'evalServiceSchema' endpoint

lib/build-clan/interface.nix

@@ -174,6 +174,7 @@ in
           inventoryFile = lib.mkOption { type = lib.types.raw; };
           # The machine 'imports' generated by the inventory per machine
           inventoryClass = lib.mkOption { type = lib.types.raw; };
+          evalServiceSchema = lib.mkOption { };
           # clan-core's modules
           clanModules = lib.mkOption { type = lib.types.raw; };
           source = lib.mkOption { type = lib.types.raw; };

lib/build-clan/module.nix

@@ -205,6 +205,21 @@ in
 
     inherit inventoryClass;
 
+    # Endpoint that can be called to get a service schema
+    evalServiceSchema =
+      {moduleSpec}:
+      let
+        resolvedModule = clan-core.clanLib.inventory.resolveModule {
+          inherit moduleSpec;
+          flakeInputs = config.self.inputs;
+          localModuleSet = config.inventory.modules;
+        };
+      in
+      (clan-core.clanLib.inventory.evalClanService {
+        modules = [ resolvedModule ];
+        prefix = [ ];
+      }).config.result.api.schema;
+
     # TODO: unify this interface
     # We should have only clan.modules. (consistent with clan.templates)
     inherit (clan-core) clanModules clanLib;