Make headline images explicit, add asset credits

- related_assets gains a `headline` boolean (DB-enforced: at most one
  per page), replacing "first image by position" as the headline
  rule. A rake task backfills the current first image on every live
  head/draft, so nothing changes visually until an editor changes it.
- The image picker sidebar gets a star toggle reflecting the flag;
  the TinyMCE inline-image picker's badge now reads it too, instead
  of assuming position 0.
- No headline chosen (or none attached) now falls back to the
  gallery-count caption itself becoming the lightbox trigger, instead
  of the gallery being unreachable.
- Assets gain creator, source_url, and license_key (against a new
  config/asset_licenses.yml dictionary). asset_credit renders a
  degrading attribution line, reused as a hidden per-image glightbox
  caption so credit is one click away for every image, not only the
  headline's always-visible one.
- Fixed: asset thumbnails rendered unconditionally regardless of
  whether a real variant exists on disk. Asset#has_variant? checks
  file existence, not content type -- some legacy PDFs have real
  pre-rewrite thumbnails a content-type check would have hidden.
- assets#new/edit rebuilt onto the same node_description/node_content
  layout as assets#show, picking up the three new fields in the
  process.

1 files changed, 11 insertions, 1 deletions

diff --git a/app/views/nodes/edit.html.erb b/app/views/nodes/edit.html.erb
index 25f15c24..2c1e9755 100644
--- a/app/views/nodes/edit.html.erb
+++ b/app/views/nodes/edit.html.erb
@@ -82,11 +82,18 @@
           <ul id="related_asset_list" class="thumbnail_list">
             <% @page.related_assets.includes(:asset).each do |related| %>
               <li data-url="<%= node_related_asset_path(@node, related) %>"
+                  data-asset-id="<%= related.asset.id %>"
                   data-large-url="<%= related.asset.upload.url(:large) %>"
                   data-original-url="<%= related.asset.upload.url %>"
-                  data-name="<%= related.asset.name %>">
+                  data-name="<%= related.asset.name %>"
+                  data-headline="<%= related.headline? %>"
+                  class="<%= "is_headline" if related.headline? %>">
                 <span class="related_asset_handle"><%= icon("grip-vertical", library: "tabler", "aria-hidden": true) %></span>
                 <%= image_tag related.asset.upload.url(:thumb) %>
+                <button type="button" class="related_asset_set_headline"
+                        aria-pressed="<%= related.headline? %>" aria-label="Set as headline image">
+                  <%= icon("star", library: "tabler", "aria-hidden": true) %>
+                </button>
                 <button type="button" class="related_asset_remove" aria-label="Remove image">
                   <%= icon("x", library: "tabler", "aria-hidden": true) %>
                 </button>
@@ -102,6 +109,9 @@
         <li>
           <span class="related_asset_handle"><%= icon("grip-vertical", library: "tabler", "aria-hidden": true) %></span>
           <img src="">
+          <button type="button" class="related_asset_set_headline" aria-pressed="false" aria-label="Set as headline image">
+            <%= icon("star", library: "tabler", "aria-hidden": true) %>
+          </button>
           <button type="button" class="related_asset_remove" aria-label="Remove image">
             <%= icon("x", library: "tabler", "aria-hidden": true) %>
           </button>