Gate live-content changes on restricted surfaces

publish_draft!, trash!, destroy_from_trash!, attach_asset! and
Asset#destroy_witnessed! now refuse unless the acting user holds redaktion,
and only when the subject is on a restricted surface: the front page, the
updates tree that feeds ~100k subscribers, or disclosure. Drafting,
autosaving, tagging and creating stay free everywhere for everyone.

Enforcement is in the models rather than the controllers, since attach_asset!
and the rest are reachable from rake tasks and internal paths. It follows the
errors.add-plus-bare-raise pattern the rest of Node already uses, so every
existing RecordInvalid rescue reports it with a localised message; only
assets_controller#destroy needed a rescue added.

A nil user is treated as a system context and bypasses the gate. The default
nil on three of those verbs is what makes that reachable, and removing those
defaults once every call site passes a user is the next tightening.

1 files changed, 1 insertions, 0 deletions

diff --git a/lib/ccc_conventions.rb b/lib/ccc_conventions.rb
index 7ff5a3ab..b840dee2 100644
--- a/lib/ccc_conventions.rb
+++ b/lib/ccc_conventions.rb
@@ -3,6 +3,7 @@ module CccConventions
   ERFA_PARENT_NAME        = "club/erfas"
   CHAOSTREFF_PARENT_NAME  = "club/chaostreffs"
   SITEMAP_COLLAPSED_PATHS = %w[updates club/erfas club/chaostreffs disclosure].freeze
+  RESTRICTED_SUBTREES     = %w[updates disclosure].freeze
 
   NODE_KINDS = {
     "top_level" => {