WIP: Musa Bootstrapper

[dennis-tra]

This PR adds the Musa bootstrapper. It's called like that to capture the 🍌 vibes around here.

Run Jaeger with:

docker run --rm --name jaeger -p 16686:16686 -p 4317:4317 jaegertracing/all-in-one:1.49

Then just run musa with, e.g., go run musa.go. Check out the CLI options with --help.

NAME:
   musa - a lean bootstrapper for any network

USAGE:
   musa [global options] command [command options] [arguments...]

COMMANDS:
   help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --host value          the network musa should bind on (default: "127.0.0.1") [$MUSA_HOST]
   --port value          the port on which musa should listen on (default: random) [$MUSA_PORT]
   --protocol value      the libp2p protocol for the DHT (default: "/ipfs/kad/1.0.0") [$MUSA_PROTOCOL]
   --metrics-host value  the network musa metrics should bind on (default: "127.0.0.1") [$MUSA_METRICS_HOST]
   --metrics-port value  the port on which musa metrics should listen on (default: random) [$MUSA_METRICS_PORT]
   --trace-host value    the network musa trace should be pushed to (default: "127.0.0.1") [$MUSA_TRACE_HOST]
   --trace-port value    the port to which musa should push traces (default: random) [$MUSA_TRACE_PORT]
   --help, -h            show help

Notes:

• currently it only adds the other bootstrap peers to the routing table it could connect to. This means FIND_NODE responses will only contain those
• it is configured with a NullDatastore. Provider/IPNS/PK records are basically piped to /dev/null

To test it I've run:

vole dht gcp zQmSnuWmxptJZdLJpKRarxBMS2Ju2oANVrgbr2xWbie9b2D /ip4/127.0.0.1/tcp/$PORT/p2p/$MUSA_PEER_ID

zQmSnuWmxptJZdLJpKRarxBMS2Ju2oANVrgbr2xWbie9b2D is just a random CID with multibase encoding. The $MUSA_PEER_ID is printed to the console after Musa has started.

[iand]

Don't we always want a Null datastore? What's the behaviour here with a different protocol?

[dennis-tra]

If the protocol is the /ipfs/kad/1.0.0 protocol, the DHT v2 implementation will configure three backends for the provider, ipns, and pk records. Unless there's a datastore passed into the DHT configuration, we're using an in-memory leveldb datastore.

To mimic the behaviour of the rust bootstrapper I configured the null datastore to not store anything.

[dennis-tra]

As discussed, we'll move Musa to https://github.com/plprobelab/musa. I only kept the none Musa-specific changes and deleted the v2/cmd/musa/ directory.