Refactor

Moves from_json to utils and splits the models to files in a module

playlist/models/album.py

@@ -0,0 +1,12 @@
+from django.db import models
+from .artist import Artist
+
+class Album(models.Model):
+    def __str__(self):
+        return self.name
+    id = models.CharField(primary_key=True, max_length=128)
+    name = models.CharField(max_length=255)
+    artists = models.ManyToManyField(Artist)
+    album_type = models.CharField(max_length=255)
+    total_tracks = models.PositiveSmallIntegerField(null=True)
+    image = models.ImageField(upload_to="albums/")