Added song/artist and album/artist synchronization

app/src/main/java/com/cappielloantonio/play/model/AlbumArtistCross.java

@@ -0,0 +1,61 @@
+package com.cappielloantonio.play.model;
+
+import androidx.annotation.NonNull;
+import androidx.room.ColumnInfo;
+import androidx.room.Entity;
+import androidx.room.PrimaryKey;
+
+@Entity(tableName = "album_artist_cross")
+public class AlbumArtistCross {
+    @NonNull
+    @PrimaryKey(autoGenerate = true)
+    @ColumnInfo(name = "id")
+    private int id;
+
+    @ColumnInfo(name = "album_id")
+    private String albumId;
+
+    @ColumnInfo(name = "artist_id")
+    private String artistId;
+
+    @ColumnInfo(name = "is_producer")
+    private boolean isProducer;
+
+    public AlbumArtistCross(String albumId, String artistId, boolean isProducer) {
+        this.albumId = albumId;
+        this.artistId = artistId;
+        this.isProducer = isProducer;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public String getAlbumId() {
+        return albumId;
+    }
+
+    public void setAlbumId(String albumId) {
+        this.albumId = albumId;
+    }
+
+    public String getArtistId() {
+        return artistId;
+    }
+
+    public void setArtistId(String artistId) {
+        this.artistId = artistId;
+    }
+
+    public boolean isProducer() {
+        return isProducer;
+    }
+
+    public void setProducer(boolean producer) {
+        isProducer = producer;
+    }
+}