Added artist, album, and song models to the homepage app

homepage/models.py

 from django.db import models
 
 # Create your models here.
+# *Artist
+#  *   artist_name
+#   *  monthly_listeners
+
+# * Album
+#     * album_name
+#     * artist
+#     * description
+#     * release_date
+
+# * Song
+#     * song_title
+#     * artist
+#     * album
+#     * song_length
+class Artist(models.Model):
+    artist_name = models.CharField()
+    monthly_listeners = models.IntegerField()
+
+class Album(models.Model):
+    album_name = models.CharField()
+    artist = models.ForeignKey(Artist)
+    description = models.CharField()
+    release_date = models.IntegerField()
+
+class Song(models.Model):
+    song_title = models.CharField()
+    artist  = models.ForeignKey(Artist)
+    album = models.ForeignKey(Album)
+    song_length = models.IntegerField()
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