[2SP, 2SP] Service: Ensure signal metadata is propagated from source in the remote flowgraph via the RemoteSource to the local flowgraph

[frankosterfeld]

• Make sure graph prototype correctly handles metadata, see also Fix propagation of signal metadata by DataSink gnuradio4#285
• Make sure that metadata (sample rate, signal name, signal unit, signal min, signal max) is propagated all the way from the respective settings at the GR source block via the GR data sink to the REST payload sent by the GnuRadioWorker.
• Ensure that metadata sent by the GnuRadioWorker service and received by RemoteSource is forwarded correctly down the line to other blocks/charts, etc.

[frankosterfeld]

#164 is ready, but depends on:

fair-acc/gnuradio4#283 (ready from my POV, open question about renaming existing init() function or state machine callback)

fair-acc/gr-digitizers#142 (code ready, but dependency needs to be updated after merge of fair-acc/gnuradio4#283)