Clear up old Actions logs (#31735)

Part of #24256.

Clear up old action logs to free up storage space.

Users will see a message indicating that the log has been cleared if
they view old tasks.

<img width="1361" alt="image"
src="https://github.com/user-attachments/assets/9f0f3a3a-bc5a-402f-90ca-49282d196c22">

Docs: https://gitea.com/gitea/docs/pulls/40

---------

Co-authored-by: silverwind <me@silverwind.io>

models/migrations/migrations.go

@@ -595,6 +595,8 @@ var migrations = []Migration{
 	NewMigration("Add force-push branch protection support", v1_23.AddForcePushBranchProtection),
 	// v301 -> v302
 	NewMigration("Add skip_secondary_authorization option to oauth2 application table", v1_23.AddSkipSecondaryAuthColumnToOAuth2ApplicationTable),
+	// v302 -> v303
+	NewMigration("Add index to action_task stopped log_expired", v1_23.AddIndexToActionTaskStoppedLogExpired),
 }
 
 // GetCurrentDBVersion returns the current db version

models/migrations/v1_23/v302.go

@@ -0,0 +1,18 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_23 //nolint
+
+import (
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm"
+)
+
+func AddIndexToActionTaskStoppedLogExpired(x *xorm.Engine) error {
+	type ActionTask struct {
+		Stopped    timeutil.TimeStamp `xorm:"index(stopped_log_expired)"`
+		LogExpired bool               `xorm:"index(stopped_log_expired)"`
+	}
+	return x.Sync(new(ActionTask))
+}