Feature: sdbusplus match object could allow owning captures

[edtanous]

This feature requests is best described with code examples. When using a match today that uses lambdas, I have to write the following code:

std::function<void(sdbusplus::message::message&)> handler = [](sdbusplus::message::message& m){
   /// Do something with m.
};

sdbusplus::bus::match::match myMatch(bus, "MATCH EXPRESSION", handler);

This can be somewhat problematic as the handler variable needs its lifecycle managed elsewhere, which may or may not cause problems, and leads to quite a bit of boilerplate code that could be handled with RAII.

The code i WANT to write, is this:

sdbusplus::bus::match::match myMatch(bus, "MATCH EXPRESSION",  [](sdbusplus::message::message& m){
   /// Do something with m.
});

Where the handler lifetime has now been tied to the match object, and there's no explicit destruction or lifetime management required. This similar pattern is supported in a lot of the ASIO stuff, by type erasing the handler, and providing a template overload of the match object constructor, and storing the state internally in the match object. Another option would be to provide a std::function overload, although less efficient, would allow attaching any sort of state that's needed to the match object. When the match is destroyed, so is the handler.