Require explicit decorator on one arg constructors

We essentially follow this rule already, not relying on implicit
operators, although there are a number of cases where in theory we
could've implicitly constructed an object.

This commit enables the clang-tidy check.

Tested: Code compiles, passes clang-tidy.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: Ia428463313b075c69614fdb326e8c5c094e7adde
diff --git a/redfish-core/include/redfish.hpp b/redfish-core/include/redfish.hpp
index c961b2d..8c05dd7 100644
--- a/redfish-core/include/redfish.hpp
+++ b/redfish-core/include/redfish.hpp
@@ -62,7 +62,7 @@
      *
      * @param[in] app   Crow app on which Redfish will initialize
      */
-    RedfishService(App& app)
+    explicit RedfishService(App& app)
     {
         requestAccountServiceRoutes(app);
         requestRoutesRoles(app);