Throw json schema validator exception by default

[Leon0402]

Hi,

I noticed that the library by default just throws std::invalid_argument here

json-schema-validator/src/json-validator.cpp

Line 1302 in 89ed13d

throw std::invalid_argument(std::string("At ") + ptr.to_string() + " of " + instance.dump() + " - " + message + "\n");

.

I don't want to catch std::invalid_argument. I know I can provide my own error handler, but it looks identical to the default one except that it throws a subclass of std::invalid_argument.
So I wonder if the lib itself could not just do that by default?

A second thing I wondered:

json-schema-validator/src/nlohmann/json-schema.hpp

Line 142 in 89ed13d

virtual void error(const json::json_pointer & /*ptr*/, const json & /*instance*/, const std::string & /*message*/) = 0;

Couldn't this member function made const and therefore every argument of validate made const too? This would allow to pass RValue to validate().

So validate(j, MyHandler {});

[pboettch]

Thanks for these ideas.

I haven't spent a lot of time thinking about exception-customization. I like your idea. Please issue a PR with an according change (also because I wouldn't know how to do it correctly).

Regarding constness, if there is something which is not const, but should be const, go ahead and make a PR. Especially if it improves the overall usage.