Allow to update configuration and inform subscribers via handlers

examples/example01/Dockerfile.debug

examples/example01/cmd/start.go

examples/example01/handlers/interfaces/interfacesHandler.go

...le01/handlers/network-instances/networkInstanceHandler.go

examples/example01/handlers/system/hostnameHandler.go

examples/example01/handlers/system/memoryHandler.go

examples/example01/handlers/system/motdHandler.go

examples/example01/handlers/system/stateHandler.go

examples/example01/handlers/system/systemHandler.go

examples/example01/target.Dockerfile

go.mod

go.sum

handler/handler.go

internal/gnmiserver/server.go

internal/gnmiserver/subscribe.go

internal/gnmiserver/util.go

internal/notifications/notifications.go

target.go