Add transport command to leshan-client-demo

[sbernard31]

This is experimentation about adding a transport command to leshan-client-demo to be able to configure transport layer.

This looks like :

Usage: leshan-client-demo transport [-h] [COMMAND]
Configure Leshan transport layer. Can be used to add, remove or use different
implementation of supported LWM2M transport.

By default, Californium library is used for coap/coaps. Some Californium
parameters can be tweaked in Californium3.client.properties file.
Default behavior is like using :
transport californium coap coaps

More examples :
coaps support only based on Californium library :
transport californium coaps

coap support based on java-coap library :
transport java-coap coap

coaps support based on Californium library and coap support based java-coap
library:
transport californium coaps java-coap coap

Launch transport [californium|java-coap] -h for more details.

  -h, --help   Display help information.
Commands:
  californium  Configure transport based on Californium.
  java-coap    Configure transport based on java-coap.

This could sound a bit overkill but this will allow to have specific option for each transport.
E.g. connection id option should probably be moved have a transport californium coaps option

[sbernard31]

❌ Bad news, picocli behavior is not what I expected and so this way to go will not work... 😬

See : remkop/picocli#2133 for more details.

For now I didn't find any alternative... 😞