- various __all__

- serializer: track search, reorder module files
- autocomplete: allow simple string value selection
- playlist editor:
    - ui & flow improve
    - init data
    - save user settings
    - autocomplete
    - fix bugs
    - discard changes

aircox/models/user_settings.py

@@ -0,0 +1,16 @@
+from django.db import models
+from django.contrib.auth.models import User
+from django.utils.translation import gettext_lazy as _
+
+
+class UserSettings(models.Model):
+    """
+    Store user's settings.
+    """
+    user = models.OneToOneField(
+        User, models.CASCADE, verbose_name=_('User'),
+        related_name='aircox_settings')
+    playlist_editor_columns = models.JSONField(
+        _('Playlist Editor Columns'))
+    playlist_editor_sep = models.CharField(
+        _('Playlist Editor Separator'), max_length=16)