feat: Add Promise-based callServiceAsync wrapper for async/await support

[ikwilnaarhuisman]

Public API Changes
Added callServiceAsync with a promise return. Which allows for cleaner usage.

for example: (response based on default srv implementation from: (https://github.com/ros2/common_interfaces/tree/rolling/std_srvs/srv)

// Originally:
service.callService(
  request,
  (response) => {
    if (response.success) {
      console.log("request successful");
    } else {
      console.error("request failed");
    }
  },
  (failedCallbackString) => {
    console.error("request failed");
  }
);

// Which now may be replaced with:
try {
  const response = await service.callServiceAsync(request);
  
  if (response.success) {
    console.log("request successful");
  } else {
    console.error("request failed");
  }
} catch (error) {
  console.error("request failed");
}

In my opinion this is a lot more readable and a bit more normalized in the "typescript / javascript" world.

[ikwilnaarhuisman]

added a unit test (or integration test... whatever you'd like to call it) based on the https://docs.ros.org/en/hydro/api/rosapi/html/srv/GetTime.html

Which I think is nice considering we'll probably always be using the rosbridge, right?

[ikwilnaarhuisman]

Shit! Seems that ros1 does not support the getTime service from rosapi, should I make the unit test limited to ROS_VERSION 2. Considering everything's sourced well you can easily get that environment variable. LMK!

[EzraBrooks]

This is a great contribution! I had done this as a wrapper of callService in my previous project, having it in the core library will be very useful.

For the test, what about creating a service server in the test code itself and then calling that?

[ikwilnaarhuisman]

This is a great contribution! I had done this as a wrapper of callService in my previous project, having it in the core library will be very useful.

lmao:

For the test, what about creating a service server in the test code itself and then calling that?

Sure! I'll take a gander at how it's done with the other unit tests and push ASAP.

[ikwilnaarhuisman]

Hooray