feat: move storage path setting to configuration file

- change default storage path to /srv/libretime
- remove music dirs table
- use /tmp for testing storage
- storage dir should always have a trailing slash

api/libretime_api/storage/serializers/__init__.py

@@ -1,4 +1,3 @@
 from .cloud_file import CloudFileSerializer
 from .file import FileSerializer
-from .storage import MusicDirSerializer
 from .track_type import TrackTypeSerializer

api/libretime_api/storage/serializers/storage.py

@@ -1,9 +0,0 @@
-from rest_framework import serializers
-
-from ..models import MusicDir
-
-
-class MusicDirSerializer(serializers.HyperlinkedModelSerializer):
-    class Meta:
-        model = MusicDir
-        fields = "__all__"