hosted version of roboreg with roboreg_nodes as client

[mhubii]

Given the roboreg_nodes cannot be distributed through the ROS buildfarm (ros/rosdistro#44677, roboreg pip wheels not accessible for apt), one may consider implementing a version of the roboreg_nodes as a client to some hosted version of roboreg.

This would allow distribution of this package by effectively de-coupling dependencies.

Package could be along the lines of roboreg_cloud_client

[mhubii]

For reference and as discussed @Haydnspass. Currently:

roboreg (PyPI distributed Python library)
     ^
     |
ros2_roboreg
  |_ roboreg_idl (apt-get distributable, provides the client-server interface definition language IDL)
  |_ roboreg_nodes (*not* apt-get distributable, implements a server for ROS)
  |_ roboreg_rviz (apt-get distributable, acts as a client to roboreg_nodes)

Ideally roboreg_nodes would act as a client to a hosted version of roboreg. Even better, an intermediate layer would avoid any ROS dependency but make it optional. E.g.

roboreg (PyPI distributed Python library, has some ROS dependency, albeit abstracted, for parsing STL files, well manageable on a hosted instance)
     ^
     |
Host (AWS, Azure, ...)
     ^
     |
REST API (supporting any form of client)
     ^
     |_ website client (demo purposes)
     |
     |_ ros2_roboreg
          |_ roboreg_idl (apt-get distributable, provides the client-server interface definition language IDL)
          |_ roboreg_nodes (apt-get distributable, implements a client to the REST API and acts as a server for ROS)
          |_ roboreg_rviz (apt-get distributable, acts as a client to roboreg_nodes)

Just as an initial draft. It should be briefly assessed whether rosbridge_suite may meet some of these requirements.

If of interest @maxboels.