Add typed connections/edges (ADR-028, ADR-029, ADR-030)

[ERnsTL]

• TODO what format to use for more structured message contents? ASN.1, grpc, thrift, XML, JSON, ..?
• TODO how to allow component to select the message format it wants to use?
• Also relevant: issue Ability to use non-JSON packet format(s) #143 ability to use non-JSON packet formats