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/models/storage.py

@@ -0,0 +1,12 @@
+from django.db import models
+
+
+class MusicDir(models.Model):
+    directory = models.TextField(unique=True, blank=True, null=True)
+    type = models.CharField(max_length=255, blank=True, null=True)
+    exists = models.BooleanField(blank=True, null=True)
+    watched = models.BooleanField(blank=True, null=True)
+
+    class Meta:
+        managed = False
+        db_table = "cc_music_dirs"