feat: add discovery

Signed-off-by: kjuulh <contact@kjuulh.io>

crates/churn/src/server/config.rs

@@ -0,0 +1,7 @@
+#[derive(clap::Args)]
+pub struct ServerConfig {
+    #[arg(long = "external-host", env = "EXTERNAL_HOST")]
+    pub external_host: String,
+    #[arg(long = "process-host", env = "PROCESS_HOST")]
+    pub process_host: String,
+}