feat(middleware/alert): private method to clear alert sourcec last run

Ticket:	#78214

src/middlewared/middlewared/plugins/alert.py

@@ -1,6 +1,7 @@
 from collections import defaultdict
 import copy
 from datetime import datetime
+import errno
 import os
 import traceback
 
@@ -463,6 +464,14 @@ async def oneshot_delete(self, job, source, query):
 
         await self.middleware.call("alert.send_alerts")
 
+    @private
+    def alert_source_clear_run(self, name):
+        alert_source = ALERT_SOURCES.get(name)
+        if not alert_source:
+            raise CallError("Alert source {name!r} not found.", errno.ENOENT)
+
+        self.alert_source_last_run[alert_source.name] = datetime.min
+
 
 class AlertServiceService(CRUDService):
     class Config: