fix(model-server): use invariantSeparatorsPath to allow running model-server on windows

Author: nkoester

model-server/src/main/kotlin/org/modelix/model/server/Main.kt

@@ -245,7 +245,7 @@ object Main {
                         }
                     } else {
                         // we serve the public API to the outside via swagger UI
-                        swaggerUI(path = "swagger", swaggerFile = ResourceUtils.getFile("api/model-server.yaml").path.toString())
+                        swaggerUI(path = "swagger", swaggerFile = ResourceUtils.getFile("api/model-server.yaml").invariantSeparatorsPath)
                     }
                 }
             }