Allow force push to protected branches (#28086) (migration v300)

Fixes #22722

Currently, it is not possible to force push to a branch with branch
protection rules in place. There are often times where this is necessary
(CI workflows/administrative tasks etc).

The current workaround is to rename/remove the branch protection,
perform the force push, and then reinstate the protections.

Provide an additional section in the branch protection rules to allow
users to specify which users with push access can also force push to the
branch. The default value of the rule will be set to `Disabled`, and the
UI is intuitive and very similar to the `Push` section.

It is worth noting in this implementation that allowing force push does
not override regular push access, and both will need to be enabled for a
user to force push.

This applies to manual force push to a remote, and also in Gitea UI
updating a PR by rebase (which requires force push)

This modifies the `BranchProtection` API structs to add:
- `enable_force_push bool`
- `enable_force_push_whitelist bool`
- `force_push_whitelist_usernames string[]`
- `force_push_whitelist_teams string[]`
- `force_push_whitelist_deploy_keys bool`

<img width="943" alt="image"
src="https://github.com/go-gitea/gitea/assets/79623665/7491899c-d816-45d5-be84-8512abd156bf">

branch `test` being a protected branch:

![image](https://github.com/go-gitea/gitea/assets/79623665/e018e6e9-b7b2-4bd3-808e-4947d7da35cc)
<img width="1038" alt="image"
src="https://github.com/go-gitea/gitea/assets/79623665/57ead13e-9006-459f-b83c-7079e6f4c654">

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
(cherry picked from commit 12cb1d2998f2a307713ce979f8d585711e92061c)

models/migrations/migrations.go

@@ -593,6 +593,8 @@ var migrations = []Migration{
 
 	// v299 -> v300
 	NewMigration("Add content version to issue and comment table", v1_23.AddContentVersionToIssueAndComment),
+	// v300 -> v301
+	NewMigration("Add force-push branch protection support", v1_23.AddForcePushBranchProtection),
 }
 
 // GetCurrentDBVersion returns the current db version

models/migrations/v1_23/v300.go

@@ -0,0 +1,17 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_23 //nolint
+
+import "xorm.io/xorm"
+
+func AddForcePushBranchProtection(x *xorm.Engine) error {
+	type ProtectedBranch struct {
+		CanForcePush                 bool    `xorm:"NOT NULL DEFAULT false"`
+		EnableForcePushAllowlist     bool    `xorm:"NOT NULL DEFAULT false"`
+		ForcePushAllowlistUserIDs    []int64 `xorm:"JSON TEXT"`
+		ForcePushAllowlistTeamIDs    []int64 `xorm:"JSON TEXT"`
+		ForcePushAllowlistDeployKeys bool    `xorm:"NOT NULL DEFAULT false"`
+	}
+	return x.Sync(new(ProtectedBranch))
+}