Replace daogrp handling with arc-aware version

Fixes #530

In <daogrp>s, xlink:actuate and xlink:show attributes related to the
<daoloc> can be (must be, according to standard) located on <arc>
elements within the <daogrp>, connected via:

  arc#xlink:to -> daoloc#xlink:label

They're at the same level of nesting and have no ordering guarantees, so
this code stops at the <daogrp>, constructs a fragment from its inner_xml,
and processes the whole <daogrp> at once.

This commit also includes a partial improvement to title handling, in
that it looks for an explicit title on the <daogrp>

backend/app/converters/ead_converter.rb

@@ -783,30 +783,51 @@ def make_nested_note(note_name, tag)
 
     with 'daogrp' do
       title = ''
-      ancestor(:resource, :archival_object ) { |ao| title << ao.title + ' Digital Object' }
+
+      unless title = att('title')
+        ancestor(:resource, :archival_object ) { |ao| title << ao.title + ' Digital Object' }
+      end
 
       make :digital_object, {
         :digital_object_id => SecureRandom.uuid,
         :title => title,
        } do |obj|
          ancestor(:resource, :archival_object) do |ao|
           ao.instances.push({'instance_type' => 'digital_object', 'digital_object' => {'ref' => obj.uri}})
-        end
-      end
+         end
 
-    end
+         # Actuate and Show values applicable to <daoloc>s can come from <arc> elements,
+         # so daogrp contents need to be handled together
+         dg_contents = Nokogiri::XML::DocumentFragment.parse(inner_xml)
 
+         # Hashify arc attrs keyed by xlink:to
+         arc_by_to_val = dg_contents.xpath('arc').map {|arc|
+           if arc['xlink:to']
+             [arc['xlink:to'], arc]
+           else
+             nil
+           end
+         }.reject(&:nil?).reduce({}) {|hsh, (k, v)| hsh[k] = v;hsh}
 
-   with 'daoloc' do
-     ancestor(:digital_object) do |dobj|
-      dobj.file_versions << {
-       :file_uri => att('href'),
-       :xlink_show_attribute => att('show'),
-       :file_format_name => att('role')
-       }
-     end
-   end
 
+         dg_contents.xpath('daoloc').each do |daoloc|
+           arc = arc_by_to_val[daoloc['xlink:label']] || {}
+
+           fv_attrs = {}
+
+           # attrs on <arc>
+           fv_attrs[:xlink_show_attribute] = arc['xlink:show'] if arc['xlink:show']
+           fv_attrs[:xlink_actuate_attribute] = arc['xlink:actuate'] if arc['xlink:actuate']
+
+           # attrs on <daoloc>
+           fv_attrs[:file_uri] = daoloc['xlink:href'] if daoloc['xlink:href']
+           fv_attrs[:use_statement] = daoloc['xlink:role'] if daoloc['xlink:role']
+
+           obj.file_versions << fv_attrs
+         end
+         obj
+      end
+    end
   end