Add getNetwork to soroban serve for consistency (#386)

* Add getNetwork to soroban serve for consistency

* Fix rust

* Appease clippy

cmd/soroban-cli/src/serve.rs

@@ -140,6 +140,7 @@ async fn handler(
         ("getAccount", Some(Requests::StringArg(b))) => get_account(b),
         ("getHealth", Some(Requests::NoArg()) | None) => Ok(get_health()),
         ("getLedgerEntry", Some(Requests::StringArg(key))) => get_ledger_entry(key, &ledger_file),
+        ("getNetwork", Some(Requests::NoArg())) => Ok(get_network()),
         ("getTransactionStatus", Some(Requests::StringArg(b))) => {
             get_transaction_status(&transaction_status_map, b).await
         }
@@ -215,6 +216,13 @@ fn get_ledger_entry(k: Box<[String]>, ledger_file: &PathBuf) -> Result<Value, Er
     }
 }
 
+fn get_network() -> Value {
+    json!({
+        "passphrase": SANDBOX_NETWORK_PASSPHRASE,
+        "protocolVersion": 20,
+    })
+}
+
 fn parse_transaction(
     txn_xdr: &str,
     passphrase: &str,