[REQ] [C++][Pistache] Header guards not unique

The code generated by the C++ pistache generator includes header guards in each header. The name of these header guards are based only on the class contained within the header. E.g.:

#ifndef Animal_H_
#define Animal_H_

namespace a {
namespace b {

class Animal {
};

}
}

#endif /* Animal_H_ */

Such header guards can easily conflict with guards in existing code (which could come from another library, e.g. imagine a class named vector, which exists in tons of libraries).

I would suggest including at least each of the namespaces in the header guard variable's name (i.e. #ifndef a_b_Animal_H_). Or, IMHO even better, use #pragma once which avoids the whole issue altogether.

Start by locating the C++ Pistache generator templates or entry points that emit header guards, then inspect generated headers like the Animal example. Confirm that guards remain unique when classes share names across namespaces; done means the generated guards include sufficient namespace context or use pragma once, with the resulting generated output checked for conflicts.