feat!: Abusive content reporting (#6977)

This implements milestones 1. and 4. from **Task F. Moderation features: Reporting** (part of [amendment of the workplan](https://codeberg.org/forgejo/sustainability/src/branch/main/2022-12-01-nlnet/2025-02-07-extended-workplan.md#task-f-moderation-features-reporting) for NLnet 2022-12-035):

> 1. A reporting feature is implemented in the database. It ensures that content remains available for review, even if a user deletes it after a report was sent.

> 4. Users can report the most relevant content types (at least: issue comments, repositories, users)

### See also:
- forgejo/discussions#291
- forgejo/discussions#304
- forgejo/design#30

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/6977
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Reviewed-by: Otto <otto@codeberg.org>
Co-authored-by: floss4good <floss4good@disroot.org>
Co-committed-by: floss4good <floss4good@disroot.org>

models/user/user.go

@@ -153,6 +153,9 @@ type User struct {
 	KeepActivityPrivate bool   `xorm:"NOT NULL DEFAULT false"`
 	KeepPronounsPrivate bool   `xorm:"NOT NULL DEFAULT false"`
 	EnableRepoUnitHints bool   `xorm:"NOT NULL DEFAULT true"`
+
+	// If you add new fields that might be used to store abusive content (mainly string fields),
+	// please also add them in the UserData struct and the corresponding constructor.
 }
 
 func init() {
@@ -610,6 +613,7 @@ var (
 		"pulls",
 		"milestones",
 		"notifications",
+		"report_abuse",
 
 		"favicon.ico",
 		"manifest.json", // web app manifests
@@ -919,6 +923,12 @@ func UpdateUserCols(ctx context.Context, u *User, cols ...string) error {
 		return err
 	}
 
+	// If the user was reported as abusive and any of the columns being updated is relevant
+	// for moderation purposes a shadow copy should be created before first update.
+	if err := IfNeededCreateShadowCopyForUser(ctx, u, cols...); err != nil {
+		return err
+	}
+
 	_, err := db.GetEngine(ctx).ID(u.ID).Cols(cols...).Update(u)
 	return err
 }