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, 24 insertions, 5 deletions

diff --git a/app/helpers/content_helper.rb b/app/helpers/content_helper.rb
index 58109664..5b672598 100644
--- a/app/helpers/content_helper.rb
+++ b/app/helpers/content_helper.rb
@@ -53,11 +53,8 @@ module ContentHelper
   end
 
   def headline_image
-    @images = @page.assets.images
-
-    unless @images.empty?
-      render :partial => 'content/headline_image'
-    end
+    @headline_asset = @page.related_assets.find_by(headline: true)&.asset
+    render :partial => 'content/headline_image' if @headline_asset || @page.assets.images.any?
   end
 
   # Returns the published_at attribute of a page if it is not nil, otherwise
@@ -154,4 +151,26 @@ module ContentHelper
     )
   end
 
+  def asset_credit(asset)
+    return nil unless asset
+    return nil if asset.creator.blank? && asset.source_url.blank? && asset.license_key.blank?
+
+    license = AssetLicense.find(asset.license_key)
+
+    photo_label = t("asset_credits.photo", name: asset.name)
+    photo = asset.source_url.present? ? link_to(photo_label, asset.source_url) : photo_label
+
+    attribution_parts = [photo]
+    attribution_parts << t("asset_credits.by", creator: asset.creator) if asset.creator.present?
+    attribution = safe_join(attribution_parts, " ")
+
+    license_text = if license
+      name = t("asset_licenses.#{license.key}", default: license.key)
+      phrase = license.style == "license" ? t("asset_credits.licensed_under", license: name) : name
+      license.url.present? ? link_to(phrase, license.url) : phrase
+    end
+
+    full = license_text ? safe_join([attribution, license_text], ", ") : attribution
+    safe_join([full, "."])
+  end
 end