Fetch next queued song (#125)

* Added code

* Got it working

* Added test and refactored test code

* Removed comment

* Cleanup

* Code formatting

src/callers/mod.rs

@@ -3,6 +3,7 @@ pub mod song;
 
 pub mod endpoints {
     pub const QUEUESONG: &str = "/api/v2/song/queue";
+    pub const QUEUESONGDATA: &str = "/api/v2/song/queue/{id}";
     pub const NEXTQUEUESONG: &str = "/api/v2/song/queue/next";
     pub const QUEUEMETADATA: &str = "/api/v2/song/metadata/queue";
 }