refactor sync server to use pluggable storage

..with a fixed implementation of the replica / server protocol logic.
There isn't much logic yet, and there's a lot of boilerplate to take
care of, so this looks a little lopsided, but I'm confident this is the
right structure for this code's future.

sync-server/src/main.rs

@@ -1,12 +1,10 @@
+use crate::storage::{InMemoryStorage, Storage};
 use actix_web::{get, web, App, HttpServer, Responder, Scope};
 use api::{api_scope, ServerState};
-use server::{InMemorySyncServer, SyncServer};
 
 mod api;
 mod server;
-
-#[cfg(test)]
-mod test;
+mod storage;
 
 // TODO: use hawk to sign requests
 
@@ -27,7 +25,7 @@ pub(crate) fn app_scope(server_state: ServerState) -> Scope {
 
 #[actix_web::main]
 async fn main() -> std::io::Result<()> {
-    let server_box: Box<dyn SyncServer> = Box::new(InMemorySyncServer::new());
+    let server_box: Box<dyn Storage> = Box::new(InMemoryStorage::new());
     let server_state = ServerState::new(server_box);
 
     HttpServer::new(move || App::new().service(app_scope(server_state.clone())))
@@ -35,3 +33,22 @@ async fn main() -> std::io::Result<()> {
         .run()
         .await
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::api::ServerState;
+    use crate::storage::{InMemoryStorage, Storage};
+    use actix_web::{test, App};
+
+    #[actix_rt::test]
+    async fn test_index_get() {
+        let server_box: Box<dyn Storage> = Box::new(InMemoryStorage::new());
+        let server_state = ServerState::new(server_box);
+        let mut app = test::init_service(App::new().service(app_scope(server_state))).await;
+
+        let req = test::TestRequest::get().uri("/").to_request();
+        let resp = test::call_service(&mut app, req).await;
+        assert!(resp.status().is_success());
+    }
+}