Auth for exporting traces

[RebeccaMahany]

Adds a gRPC wrapper that adds a bearer auth header to all outgoing trace exports. Also allows the ingest server URL and the export traces flag to be set by the control server.

sequenceDiagram
    Participant Control server
    Box Launcher
        Participant Control service
        Participant Agent flags subsystem
        Participant Auth token subsystem
        Participant Traces exporter
    end
    Participant Agent collector

    loop Config generation
        Control server ->> Control server: Generate JWT with TTL of 24 hours
        Control service ->> Control server: Perform regular check to see if subsystem data has changed
        Control server ->> Control service: Return config, including JWT
    end

    opt Ingest URL update
        Control service ->> Agent flags subsystem: Perform update
        Agent flags subsystem ->> Traces exporter: Notify that URL has changed
        Traces exporter ->> Traces exporter: Init new exporter using new ingest URL
    end

    opt Token update
        Control service ->> Auth token subsystem: Perform update
        Auth token subsystem ->> Auth token subsystem: Store new token
        Control service ->> Traces exporter: Ping
        Traces exporter ->> Auth token subsystem: Fetch new token
        Traces exporter ->> Traces exporter: Replace token used for export
    end

    Traces exporter ->> Agent collector: Send traces with bearer auth header to stored ingest URL
    
    Agent collector ->> Agent collector: Validate JWT
    Agent collector ->> Agent collector: Process and store traces

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[directionless]

This makes sense to me, but I think it would benefit from the addition of SetNewToken(token string)

That would allow the token to be updated, without create a new exporter.

[directionless]

I suspect it would be super clean to create one, and register it with knapsack.RegisterChangeObserver

Maybe pull that into New(k knapsack)? Not sure...

[RebeccaMahany]

Yes, definitely cleaner! I'll update

[RebeccaMahany]

This is updated -- I ended up making TraceExporter subscribe to the ingest updates, and swap in the token when pinged.

[James-Pickett]

nice!

[James-Pickett]

awesome sauce