Implement ghost comment mitigation (#14349)

* Implement ghost comment mitigation

Adds a config option USER_DELETE_WITH_COMMENTS_MAX_DAYS to the [service] section. See https://codeberg.org/Codeberg/Discussion/issues/24 for the underlying issue.

* cleanup

* use setting module correctly

* add to docs

Co-authored-by: Moritz Marquardt <git@momar.de>

templates/user/settings/account.tmpl

@@ -173,6 +173,9 @@
 		<div class="ui attached error segment">
 			<div class="ui red message">
 				<p class="text left">{{svg "octicon-alert"}} {{.i18n.Tr "settings.delete_prompt" | Str2html}}</p>
+				{{ if .UserDeleteWithComments }}
+				<p class="text left" style="font-weight: bold;">{{.i18n.Tr "settings.delete_with_all_comments" .UserDeleteWithCommentsMaxDays | Str2html}}</p>
+				{{ end }}
 			</div>
 			<form class="ui form ignore-dirty" id="delete-form" action="{{AppSubUrl}}/user/settings/account/delete" method="post">
 				{{.CsrfTokenHtml}}