feat: add foreign keys to table collaboration (#9724)

This appears to be as easy as a foreign-key addition possibly could be; no automated tests required adjustments.

Manual testing conducted:
- Added collaborator to a repo
- Removed collaborator from a repo
- Deleted a repo with a collaborator on it
- Deleted a user that is a collaborator
- Verified database definitions to ensure foreign keys are present.

## Checklist

The [contributor guide](https://forgejo.org/docs/next/contributor/) contains information that will be helpful to first time contributors. There also are a few [conditions for merging Pull Requests in Forgejo repositories](https://codeberg.org/forgejo/governance/src/branch/main/PullRequestsAgreement.md). You are also welcome to join the [Forgejo development chatroom](https://matrix.to/#/#forgejo-development:matrix.org).

### Tests

- I added test coverage for Go changes...
  - [ ] in their respective `*_test.go` for unit tests.
  - [ ] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I added test coverage for JavaScript changes...
  - [ ] in `web_src/js/*.test.js` if it can be unit tested.
  - [ ] in `tests/e2e/*.test.e2e.js` if it requires interactions with a live Forgejo server (see also the [developer guide for JavaScript testing](https://codeberg.org/forgejo/forgejo/src/branch/forgejo/tests/e2e/README.md#end-to-end-tests)).

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.

### Release notes

- [ ] I do not want this change to show in the release notes.
- [x] I want the title to show in the release notes with a link to this pull request.
- [ ] I want the content of the `release-notes/<pull request number>.md` to be be used for the release notes instead of the title.

<!--start release-notes-assistant-->

## Release notes
<!--URL:https://codeberg.org/forgejo/forgejo-->
- Features
  - [PR](https://codeberg.org/forgejo/forgejo/pulls/9724): <!--number 9724 --><!--line 0 --><!--description YWRkIGZvcmVpZ24ga2V5cyB0byB0YWJsZSBjb2xsYWJvcmF0aW9u-->add foreign keys to table collaboration<!--description-->
<!--end release-notes-assistant-->

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/9724
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Mathieu Fenniak <mathieu@fenniak.net>
Co-committed-by: Mathieu Fenniak <mathieu@fenniak.net>

models/forgejo_migrations/foreign_key_utils.go

@@ -0,0 +1,31 @@
+// Copyright 2025 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package forgejo_migrations
+
+import (
+	"errors"
+
+	"forgejo.org/modules/log"
+
+	"xorm.io/xorm"
+)
+
+func syncDoctorForeignKey(x *xorm.Engine, beans []any) error {
+	for _, bean := range beans {
+		// Sync() drops indexes by default, which will cause unnecessary rebuilding of indexes when syncDoctorForeignKey
+		// is used with partial bean definitions; so we disable that option
+		_, err := x.SyncWithOptions(xorm.SyncOptions{IgnoreDropIndices: true}, bean)
+		if err != nil {
+			if errors.Is(err, xorm.ErrForeignKeyViolation) {
+				tableName := x.TableName(bean)
+				log.Error(
+					"Foreign key creation on table %s failed. Run `forgejo doctor check --all` to identify the orphaned records preventing this foreign key from being created. Error was: %v",
+					tableName, err)
+				return err
+			}
+			return err
+		}
+	}
+	return nil
+}

models/forgejo_migrations/v14a_add-foreign-keys-collaboration.go

@@ -0,0 +1,25 @@
+// Copyright 2025 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package forgejo_migrations
+
+import (
+	"xorm.io/xorm"
+)
+
+func init() {
+	registerMigration(&Migration{
+		Description: "add forgejo_migration table",
+		Upgrade:     addForeignKeysCollaboration,
+	})
+}
+
+func addForeignKeysCollaboration(x *xorm.Engine) error {
+	type Collaboration struct {
+		RepoID int64 `xorm:"UNIQUE(s) INDEX NOT NULL REFERENCES(repository, id)"`
+		UserID int64 `xorm:"UNIQUE(s) INDEX NOT NULL REFERENCES(user, id)"`
+	}
+	return syncDoctorForeignKey(x, []any{
+		new(Collaboration),
+	})
+}

models/repo/collaboration.go

@@ -19,8 +19,8 @@ import (
 // Collaboration represent the relation between an individual and a repository.
 type Collaboration struct {
 	ID          int64              `xorm:"pk autoincr"`
-	RepoID      int64              `xorm:"UNIQUE(s) INDEX NOT NULL"`
-	UserID      int64              `xorm:"UNIQUE(s) INDEX NOT NULL"`
+	RepoID      int64              `xorm:"UNIQUE(s) INDEX NOT NULL REFERENCES(repository, id)"`
+	UserID      int64              `xorm:"UNIQUE(s) INDEX NOT NULL REFERENCES(user, id)"`
 	Mode        perm.AccessMode    `xorm:"DEFAULT 2 NOT NULL"`
 	CreatedUnix timeutil.TimeStamp `xorm:"INDEX created"`
 	UpdatedUnix timeutil.TimeStamp `xorm:"INDEX updated"`