admin api: create structs for all requests/responess in src/api/admin/api.rs

src/api/admin/mod.rs

@@ -1,8 +1,24 @@
 pub mod api_server;
 mod error;
+
+pub mod api;
 mod router_v0;
 mod router_v1;
 
 mod bucket;
 mod cluster;
 mod key;
+
+use std::sync::Arc;
+
+use async_trait::async_trait;
+use serde::Serialize;
+
+use garage_model::garage::Garage;
+
+#[async_trait]
+pub trait EndpointHandler {
+	type Response: Serialize;
+
+	async fn handle(self, garage: &Arc<Garage>) -> Result<Self::Response, error::Error>;
+}