feat: Add support for both ip and hostname for peers

It is convinent to be able to specify both IPs and hostnames as peers.
Especially, when you are building ephemeral testnets and want to specify
peers as

```
./snarkos start --peers "validator0:4130,client0:4130"
```

Where you can populate the `/etc/hosts` file with subnet hostnames.

Author: Raphexion

cli/src/commands/start.rs

@@ -42,7 +42,7 @@ use rand::{Rng, SeedableRng};
 use rand_chacha::ChaChaRng;
 use serde::{Deserialize, Serialize};
 use std::{
-    net::SocketAddr,
+    net::{SocketAddr, ToSocketAddrs},
     path::PathBuf,
     sync::{Arc, atomic::AtomicBool},
 };
@@ -230,11 +230,18 @@ impl Start {
             false => Ok(self
                 .peers
                 .split(',')
-                .flat_map(|ip| match ip.parse::<SocketAddr>() {
-                    Ok(ip) => Some(ip),
-                    Err(e) => {
-                        eprintln!("The IP supplied to --peers ('{ip}') is malformed: {e}");
-                        None
+                .flat_map(|ip_or_hostname| {
+                    let trimmed = ip_or_hostname.trim();
+                    match trimmed.to_socket_addrs() {
+                        Ok(mut ip_iter) => {
+                            // A hostname might resolve to multiple IP addresses. We will use only the first one,
+                            // assuming this aligns with the user's expectations.
+                            ip_iter.next()
+                        },
+                        Err(e) => {
+                            eprintln!("The hostname or IP supplied to --peers ('{trimmed}') is malformed: {e}");
+                            None
+                        }
                     }
                 })
                 .collect()),
@@ -1046,4 +1053,60 @@ mod tests {
             panic!("Unexpected result of clap parsing!");
         }
     }
+
+    #[test]
+    fn parse_peers_when_ips() {
+        let arg_vec = vec!["snarkos", "start", "--peers", "127.0.0.1:3030,127.0.0.2:3030"];
+        let cli = CLI::parse_from(arg_vec);
+
+        if let Command::Start(start) = cli.command {
+            let peers = start.parse_trusted_peers();
+            assert!(peers.is_ok());
+            assert_eq!(peers.unwrap().len(), 2, "Expected two peers");
+        } else {
+            panic!("Unexpected result of clap parsing!");
+        }
+    }
+
+    #[test]
+    fn parse_peers_when_hostnames() {
+        let arg_vec = vec!["snarkos", "start", "--peers", "www.example.com:4130,www.google.com:4130"];
+        let cli = CLI::parse_from(arg_vec);
+
+        if let Command::Start(start) = cli.command {
+            let peers = start.parse_trusted_peers();
+            assert!(peers.is_ok());
+            assert_eq!(peers.unwrap().len(), 2, "Expected two peers");
+        } else {
+            panic!("Unexpected result of clap parsing!");
+        }
+    }
+
+    #[test]
+    fn parse_peers_when_mixed_and_with_whitespaces() {
+        let arg_vec = vec!["snarkos", "start", "--peers", "  127.0.0.1:3030,  www.google.com:4130 "];
+        let cli = CLI::parse_from(arg_vec);
+
+        if let Command::Start(start) = cli.command {
+            let peers = start.parse_trusted_peers();
+            assert!(peers.is_ok());
+            assert_eq!(peers.unwrap().len(), 2, "Expected two peers");
+        } else {
+            panic!("Unexpected result of clap parsing!");
+        }
+    }
+
+    #[test]
+    fn parse_peers_when_unknown_hostname_gracefully() {
+        let arg_vec = vec!["snarkos", "start", "--peers", "banana.cake.eafafdaeefasdfasd.com"];
+        let cli = CLI::parse_from(arg_vec);
+
+        if let Command::Start(start) = cli.command {
+            let peers = start.parse_trusted_peers();
+            assert!(peers.is_ok());
+            assert!(peers.unwrap().is_empty(), "Expected no peers to be found");
+        } else {
+            panic!("Unexpected result of clap parsing!");
+        }
+    }
 }