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/storage/router.py

@@ -0,0 +1,9 @@
+from rest_framework import routers
+
+from .views import CloudFileViewSet, FileViewSet, MusicDirViewSet, TrackTypeViewSet
+
+router = routers.DefaultRouter()
+router.register("files", FileViewSet)
+router.register("music-dirs", MusicDirViewSet)
+router.register("cloud-files", CloudFileViewSet)
+router.register("track-types", TrackTypeViewSet)