display yt-dlp version, multiple downloads enabled.

code refactoring
preparations for optimistic ui updates for new downloads

server/rest/handlers.go

@@ -158,3 +158,21 @@ func (h *Handler) DeleteTemplate() http.HandlerFunc {
 		}
 	}
 }
+
+func (h *Handler) GetVersion() http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		defer r.Body.Close()
+
+		w.Header().Set("Content-Type", "application/json")
+
+		version, err := h.service.GetVersion(r.Context())
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		if err := json.NewEncoder(w).Encode(version); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+	}
+}