deprecate helper curation_concern_page_title

we introduced a decorator in previous work, encourage users to use that
decorator directly, instead of using a simple helper.

in addition to depending less directly on model behavior (which was the initail
goal of this work, re: Valkyrie), this should better insulate downstream
applications from future helper changes. that is: applications can now change
behavior by providing a new decorator class, instead of directly overriding
helper behavior.

app/helpers/hyrax/title_helper.rb

@@ -9,13 +9,21 @@ def construct_page_title(*elements)
     (elements.flatten.compact + [application_name]).join(' // ')
   end
 
+  ##
+  # @deprecated
   def curation_concern_page_title(curation_concern)
-    Hyrax::PageTitleDecorator.new(curation_concern).page_title
+    Deprecation.warn 'The curation_concern_page_title helper will be removed in Hyrax 4.0.' \
+                     "\n\tUse title_presenter(curation_concern).page_title instead."
+    title_presenter(curation_concern).page_title
   end
 
   def default_page_title
     text = controller_name.singularize.titleize
     text = "#{action_name.titleize} " + text if action_name
     construct_page_title(text)
   end
+
+  def title_presenter(resource)
+    Hyrax::PageTitleDecorator.new(resource)
+  end
 end

app/views/hyrax/base/edit.html.erb

@@ -1,4 +1,4 @@
-<% provide :page_title, curation_concern_page_title(curation_concern) %>
+<% provide :page_title, title_presenter(curation_concern).page_title %>
 <% provide :page_header do %>
   <h1><span class="fa fa-edit" aria-hidden="true"></span><%= t("hyrax.works.update.header") %></h1>
 <% end %>

app/views/hyrax/base/new.html.erb

@@ -1,4 +1,4 @@
-<% provide :page_title, curation_concern_page_title(curation_concern) %>
+<% provide :page_title, title_presenter(curation_concern).page_title %>
 <% provide :page_header do %>
   <h1><%= t("hyrax.works.create.header", type: curation_concern.human_readable_type) %></h1>
 <% end %>

app/views/hyrax/file_sets/edit.html.erb

@@ -1,5 +1,5 @@
 <%= render "shared/nav_safety_modal" %>
-<% provide :page_title, curation_concern_page_title(curation_concern) %>
+<% provide :page_title, title_presenter(curation_concern).page_title %>
 <% provide :page_header do %>
   <h1><span class="fa fa-edit" aria-hidden="true"></span><%= t('.header', file_set: curation_concern) %></h1>
 <% end %>