feat: 添加信号signals

backend/dvadmin/system/signals.py

@@ -0,0 +1,12 @@
+from django.dispatch import Signal
+# 初始化信号
+pre_init_complete = Signal()
+detail_init_complete = Signal()
+post_init_complete = Signal()
+# 租户初始化信号
+pre_tenants_init_complete = Signal()
+detail_tenants_init_complete = Signal()
+post_tenants_init_complete = Signal()
+post_tenants_all_init_complete = Signal()
+# 租户创建完成信号
+tenants_create_complete = Signal()