Add best score in song history

back/src/history/history.service.ts

@@ -65,7 +65,7 @@ export class HistoryService {
 		});
 
 		return {
-			best: 0,
+			best: Math.max(...history.map((x) => x.score)),
 			history,
 		};
 	}

back/test/robot/history/history.robot

@@ -132,7 +132,7 @@ Get the history of a single song
     Integer    $history[1].userID    ${userID}
     Integer    $history[1].songID    ${song.body.id}
     Integer    $history[1].score    55
-    Integer    $best    0
+    Integer    $best    65
 
     [Teardown]    Run Keywords    DELETE    /users/${userID}
     ...    AND    DELETE    /song/${song.body.id}