Add Timestamped Nodes support to Send Operation at Client side

Following #1192 we decide to add Timestamped nodes to Send Operation.

The Server side part was done by #1218.

This issue aims to track / discuss about client side support.

(Here some idea about a DataCollector ? => https://github.com/eclipse/leshan/issues/1192#issuecomment-1022220554)

[adamsero]

Yeah, I think we can finally close this one now. I’m not sure about Periodic Sender’s priority right now considering #1222, but I might open it as a new issue at some point in the future. At the moment I have some side tasks but after I’m done with them we can think more about the issue.

[adamsero]

@sbernard31 OK, in 00baa08 I added DataCollector as an interface to client core and TemperatureDataCollector as a sample implementation to client demo. You can start and stop periodic read on a resource via an enabler and retrieve collected timestamped data at any time.

Right now there’s no real way to test this in practice, so I had to override send interactive command so that it passes the data collector to sendData in LeshanClient just to be able to send it to the server. Having said that, I though about proper control over data collectors:

• Add a separate interactive command that starts/stops periodic read on a specified resource (it could also create the collector, although that can be done statically in code)
• These collectors would be mapped by the resource path, so Map<LwM2mPath, DataCollector>
• Add an option to send command that causes data to be read from the collector instead of the enabler. Collector would be retrieved by the path provided by the user

Let me know what you think about my code and the ideas 🙂