Set up example use case and document

[ivalaginja]

@erinpougheon and @pbaudoz have an interest in this, so I will try to sketch out a game plan for this.

A minimal working example would constitute a testbed server that can run a camera service. This is then extendable arbitrarily to include more services. To make this work, we'd need:

1. A testbed configuration with testbed.yml
2. A CLI interface that allows the user to start the testbed server, cli_interface.py
3. A service configuration with a single service, a camera: services.yml
4. The simplest GUI viewer possible. Not sure if this should be a main window + camera viewer or just a camera viewer, but I think how we launch the GUI right now does require that.

Numbers 1-3 should probably live in a new location in the project under catkit2/examples/single_camera, outside of the package. Number 4 should probably be the start of adding GUI elements to catkit2 the package, and should go into catkit2/catkit2/user_interface. The concrete startup and setup of this would be called in the cli_interface.py of the example.

In an ideal case, a second service will be added, a simulator service which uses the already existing catkit2/simulator/simple_optical_model.py - or we create an even simpler one with literally just a light source and a camera.

@ehpor @raphaelpclt any thoughts on this? I would in particular like some feedback on the scope of the example and the location of the individual files.

[raphaelpclt]

I think that's a great idea! My intuition would be to keep all the example in one single contained location, like an testbed_example folder. I guess the goal is that someone new can copy this folder into a new repo, and start from that. This would be a "mini thd-control / hicat-package2" folder.

More specifically:

• Agreed that 1-3 go to a folder
• Wo do need a main window right now, but it shouldn't be too difficult to cut ties if needed. I wouldn't mind having a simple main window as an example too.
• I would create a new very simple optical model too, to be in the example folder.