feat(operations): job, claim and worker lease models

operations/apps.py

@@ -0,0 +1,22 @@
+from django.apps import AppConfig
+from django.db.backends.signals import connection_created
+
+
+def _sqlite_wal(sender, connection, **kwargs):
+    """The worker and gunicorn write the same SQLite file: WAL lets readers
+    go on during a write. Django's SQLite OPTIONS have no init command."""
+    if connection.vendor == "sqlite":
+        with connection.cursor() as cursor:
+            cursor.execute("PRAGMA journal_mode=WAL")
+
+
+class OperationsConfig(AppConfig):
+    default_auto_field = "django.db.models.BigAutoField"
+    name = "operations"
+
+    def ready(self):
+        connection_created.connect(_sqlite_wal)
+        # every installed app's jobs.py registers its kinds
+        from django.utils.module_loading import autodiscover_modules
+
+        autodiscover_modules("jobs")