fable: Use references instead of pointers for Conf::try_from*

This is recommended by clang-tidy as a less error prone approach.

BREAKING CHANGE:
  If you use `Conf::try_from` or `Conf::try_from_pointer`, you need
  to update your call from passing a pointer to passing a value.

  That means you may need to use one of these transformations:

    conf.try_from(key, value)       ->      conf.try_from(key, *value)
    conf.try_from(key, &value)      ->      conf.try_from(key, value)

Author: cassava

fable/include/fable/conf.hpp

@@ -258,16 +258,16 @@ class Conf {
    * - Throws a ConfError if the value is of the wrong type.
    */
   template <typename T>
-  void try_from(const std::string& key, T* val) const {
+  void try_from(const std::string& key, T& val) const {
     if (data_.count(key)) {
-      *val = get<T>(key);
+      val = get<T>(key);
     }
   }
 
   template <typename T>
-  void try_from(const JsonPointer& key, T* val) const {
+  void try_from(const JsonPointer& key, T& val) const {
     try {
-      *val = data_.at(key).get<T>();
+      val = data_.at(key).get<T>();
     } catch (nlohmann::detail::out_of_range& e) {
       return;
     } catch (nlohmann::detail::type_error& e) {
@@ -276,7 +276,7 @@ class Conf {
   }
 
   template <typename T>
-  void try_from_pointer(const std::string& key, T* val) const {
+  void try_from_pointer(const std::string& key, T& val) const {
     try_from(JsonPointer(key), val);
   }
 

plugins/basic/src/hmi_contact.hpp

@@ -194,7 +194,7 @@ class ContactMap : public Confable {
 
   void from_conf(const Conf& c) override {
     for (auto& elem : buttons_) {
-      c.try_from(elem.first, &elem.second.state);
+      c.try_from(elem.first, elem.second.state);
     }
   }