feat: add rust-libp2p-server to monorepo

Moves https://github.com/mxinden/rust-libp2p-server to the rust-libp2p monorepository.

> # Rust libp2p Server
>
> A rust-libp2p based server implementation running:
>
> - the [Kademlia protocol](https://github.com/libp2p/specs/tree/master/kad-dht)
>
> - the [Circuit Relay v2 protocol](https://github.com/libp2p/specs/blob/master/relay/circuit-v2.md)
>
> - the [AutoNAT protocol](https://github.com/libp2p/specs/blob/master/autonat/README.md)

Pull-Request: #4311.

misc/server/src/behaviour.rs

@@ -0,0 +1,78 @@
+use libp2p::autonat;
+use libp2p::identify;
+use libp2p::kad::{record::store::MemoryStore, Kademlia, KademliaConfig};
+use libp2p::ping;
+use libp2p::relay;
+use libp2p::swarm::behaviour::toggle::Toggle;
+use libp2p::{identity, swarm::NetworkBehaviour, Multiaddr, PeerId};
+use std::str::FromStr;
+use std::time::Duration;
+
+const BOOTNODES: [&str; 4] = [
+    "QmNnooDu7bfjPFoTZYxMNLWUQJyrVwtbZg5gBMjTezGAJN",
+    "QmQCU2EcMqAqQPR2i9bChDtGNJchTbq5TbXJJ16u19uLTa",
+    "QmbLHAnMoJPWSCR5Zhtx6BHJX9KiKNN6tpvbUcqanj75Nb",
+    "QmcZf59bWwK5XFi76CZX8cbJ4BhTzzA3gU1ZjYZcYW3dwt",
+];
+
+#[derive(NetworkBehaviour)]
+pub(crate) struct Behaviour {
+    relay: relay::Behaviour,
+    ping: ping::Behaviour,
+    identify: identify::Behaviour,
+    pub(crate) kademlia: Toggle<Kademlia<MemoryStore>>,
+    autonat: Toggle<autonat::Behaviour>,
+}
+
+impl Behaviour {
+    pub(crate) fn new(
+        pub_key: identity::PublicKey,
+        enable_kademlia: bool,
+        enable_autonat: bool,
+    ) -> Self {
+        let kademlia = if enable_kademlia {
+            let mut kademlia_config = KademliaConfig::default();
+            // Instantly remove records and provider records.
+            //
+            // TODO: Replace hack with option to disable both.
+            kademlia_config.set_record_ttl(Some(Duration::from_secs(0)));
+            kademlia_config.set_provider_record_ttl(Some(Duration::from_secs(0)));
+            let mut kademlia = Kademlia::with_config(
+                pub_key.to_peer_id(),
+                MemoryStore::new(pub_key.to_peer_id()),
+                kademlia_config,
+            );
+            let bootaddr = Multiaddr::from_str("/dnsaddr/bootstrap.libp2p.io").unwrap();
+            for peer in &BOOTNODES {
+                kademlia.add_address(&PeerId::from_str(peer).unwrap(), bootaddr.clone());
+            }
+            kademlia.bootstrap().unwrap();
+            Some(kademlia)
+        } else {
+            None
+        }
+        .into();
+
+        let autonat = if enable_autonat {
+            Some(autonat::Behaviour::new(
+                PeerId::from(pub_key.clone()),
+                Default::default(),
+            ))
+        } else {
+            None
+        }
+        .into();
+
+        Self {
+            relay: relay::Behaviour::new(PeerId::from(pub_key.clone()), Default::default()),
+            ping: ping::Behaviour::new(ping::Config::new()),
+            identify: identify::Behaviour::new(
+                identify::Config::new("ipfs/0.1.0".to_string(), pub_key).with_agent_version(
+                    format!("rust-libp2p-server/{}", env!("CARGO_PKG_VERSION")),
+                ),
+            ),
+            kademlia,
+            autonat,
+        }
+    }
+}