Added ability to change API port

Author: devgianlu

api/src/main/java/xyz/gianlu/librespot/api/Main.java

@@ -16,9 +16,9 @@
 public class Main {
 
     public static void main(String[] args) throws IOException, MercuryClient.MercuryException, GeneralSecurityException, Session.SpotifyAuthenticationException {
-        ApiServer server = new ApiServer(24879);
-
         AbsConfiguration conf = new FileConfiguration(args);
+
+        ApiServer server = new ApiServer(conf.getCustomOptionInt("api.port", 24879));
         if (conf.authStrategy() == AuthConfiguration.Strategy.ZEROCONF) {
             ZeroconfServer.create(conf).addSessionListener(server::restart);
         } else {

core/src/main/java/xyz/gianlu/librespot/AbsConfiguration.java

@@ -14,6 +14,8 @@
  */
 public abstract class AbsConfiguration implements TimeProvider.Configuration, Player.Configuration, CacheManager.Configuration, AuthConfiguration, ZeroconfServer.Configuration {
 
+    public abstract int getCustomOptionInt(@NotNull String key, int fallback);
+
     @Nullable
     public abstract String deviceName();
 

core/src/main/java/xyz/gianlu/librespot/FileConfiguration.java

@@ -290,6 +290,12 @@ public int releaseLineDelay() {
         return config.get("player.releaseLineDelay");
     }
 
+    @Override
+    public int getCustomOptionInt(@NotNull String key, int fallback) {
+        Integer val = config.get(key);
+        return val == null ? fallback : val;
+    }
+
     @Override
     public @Nullable String deviceName() {
         return config.get("deviceName");