feat(api): split api into multiple apps (#1626)

Fixes #1622

- split the api into 4 apps: core, history, schedule, storage
- exploded the settings into testing/prod

api/libretime_api/schedule/serializers/__init__.py

@@ -0,0 +1,21 @@
+from .playlist import PlaylistContentSerializer, PlaylistSerializer
+from .podcast import (
+    ImportedPodcastSerializer,
+    PodcastEpisodeSerializer,
+    PodcastSerializer,
+    StationPodcastSerializer,
+)
+from .schedule import ScheduleSerializer
+from .show import (
+    ShowDaysSerializer,
+    ShowHostSerializer,
+    ShowInstanceSerializer,
+    ShowRebroadcastSerializer,
+    ShowSerializer,
+)
+from .smart_block import (
+    SmartBlockContentSerializer,
+    SmartBlockCriteriaSerializer,
+    SmartBlockSerializer,
+)
+from .webstream import WebstreamMetadataSerializer, WebstreamSerializer