Resolve "State key char instead of string"

Closes #352 (closed)

include/core/utils/converter.h

@@ -94,6 +94,14 @@ struct converter<bool>{
     }
 };
 template<>
+struct converter<char>{
+    static char convert(std::string val){
+        //Here we should check that val.length() == 1 and get val[0] into a char variable
+        throw std::runtime_error("Invalid char conversion. String provided: " + val);
+    }
+};
+    //// TYPES ----> ToSTRING
+template<>
 struct converter<std::string>{
     static std::string convert(std::string val){
         return val;
@@ -109,6 +117,9 @@ struct converter<std::string>{
     static std::string convert(double val){
         return std::to_string(val);
     }
+    static std::string convert(char val){
+        return std::to_string(val);
+    }
     template<typename A>
     static std::string convert(utils::list<A> val){
         std::string result = "";