Only store in cache when OK response is received

This is a temporary workaround for
#3

src/injector.cpp

@@ -89,6 +89,28 @@ static bool ok_to_cache(const http::response_header<Fields>& hdr)
     });
 }
 
+//------------------------------------------------------------------------------
+template<class Req, class Res>
+static void try_to_cache( ipfs_cache::Injector& injector
+                        , const Req& req
+                        , const Res& res)
+{
+    if (!ok_to_cache(res)) {
+        return;
+    }
+
+    stringstream ss;
+    ss << res;
+    auto key = req.target().to_string();
+
+    injector.insert_content(key, ss.str(),
+        [key] (sys::error_code ec, auto) {
+            if (ec) {
+                cout << "!Insert failed: " << key << " " << ec.message() << endl;
+            }
+        });
+}
+
 //------------------------------------------------------------------------------
 static
 void serve( shared_ptr<GenericConnection> con
@@ -112,17 +134,14 @@ void serve( shared_ptr<GenericConnection> con
         if (ec == http::error::end_of_stream) break;
         if (ec) return fail(ec, "fetch_http_page");
 
-        if (ok_to_cache(res)) {
-            stringstream ss;
-            ss << res;
-            auto key = req.target().to_string();
-
-            injector.insert_content(key, ss.str(),
-                [key] (sys::error_code ec, auto) {
-                    if (ec) {
-                        cout << "!Insert failed: " << key << " " << ec.message() << endl;
-                    }
-                });
+        switch (res.result()) {
+            case http::status::ok:
+                try_to_cache(injector, req, res);
+                break;
+            // TODO: Other response codes
+            default:
+                cerr << "Warning: not handling: " << res.result()
+                     << " HTTP response in terms of cache" << endl;
         }
 
         // Forward back the response