refactor: make Signal to be type alias of std::string (#80)

std::string is not designed to be inherited form.
The destructor of std::string isn't virtual.

Signed-off-by: ComixHe <[email protected]>

Author: ComixHe

include/ocppi/cli/CommonCLI.hpp

@@ -31,7 +31,6 @@ struct DeleteOption;
 struct ExecOption;
 struct KillOption;
 struct ListOption;
-class Signal;
 struct StartOption;
 struct StateOption;
 struct GlobalOption;

include/ocppi/runtime/Signal.hpp

@@ -2,11 +2,7 @@
 
 #include <string>
 
-namespace ocppi::runtime
-{
-
-class Signal : public std::string {
-        using std::string::string;
-};
+namespace ocppi::runtime {
 
+using Signal = std::string;
 }

include/ocppi/runtime/SpecRuntime.hpp

@@ -10,6 +10,7 @@
 #include "ocppi/runtime/DeleteOption.hpp"
 #include "ocppi/runtime/FeaturesOption.hpp"
 #include "ocppi/runtime/KillOption.hpp"
+#include "ocppi/runtime/Signal.hpp"
 #include "ocppi/runtime/StartOption.hpp"
 #include "ocppi/runtime/StateOption.hpp"
 #include "ocppi/runtime/features/types/Features.hpp"
@@ -24,8 +25,6 @@ namespace state::types
 struct State;
 }
 
-class Signal;
-
 class SpecRuntime {
     public:
         SpecRuntime() = default;