Add erfa/chaostreff node-kind creation conventions

lib/ccc_conventions.rb: NODE_KINDS registry replaces the kind-specific
branches previously scattered across nodes_controller#create (tags),
unique_path-position check). Each kind declares its parent lookup
(a Proc - Update's "update"/"press_release" continue to genuinely
find-or-create their year-folder via Update.find_or_create_parent;
erfa/chaostreff use a plain find_by_unique_name!, since their parent
nodes are fixed and a missing one should fail loudly, not be silently
created), its tags, and (new) its default template.

Node gains a default_template_name column (migration, with backfill
for existing update-tree nodes via node.update? - reusing that method
rather than re-deriving its unique_path check in raw SQL). Page#set_template
now inherits from node.default_template_name, falling back to the old
update?-based check only when the column is blank, and only fills in
template_name when nothing's already been explicitly chosen - a
deliberate change from the previous behavior, which unconditionally
overwrote template_name on every save regardless of manual selection.
Node#update? itself is unchanged and still used as-is by
admin_controller's sitemap filtering - a genuinely different, still
valid use of that check.

"generic" stays special-cased in the controller, parametrized by
params[:parent_id] at request time - doesn't fit "kind implies a fixed
lookup" and isn't in the registry.

nodes#new's four hardcoded radio buttons and nodes_controller's
kind-specific case/when branches are both replaced by iterating/looking
up this one registry - adding a new kind now means one new hash entry,
not four scattered edits.

1 files changed, 2 insertions, 3 deletions

diff --git a/app/models/page.rb b/app/models/page.rb
index c982c2e..20461bf 100644
--- a/app/models/page.rb
+++ b/app/models/page.rb
@@ -225,9 +225,8 @@ class Page < ApplicationRecord
     end
 
     def set_template
-      if node && node.update?
-        self.template_name = "update"
-      end
+      return if template_name.present?
+      self.template_name = node&.default_template_name || (node&.update? ? "update" : nil)
     end
 
     def rewrite_links_in_body