Use alchemy_display_name for page actor names

If you have a user class that does not implement
name (eg. `Spree::User` or a generic `User` class)
it would return `nil` for Page actor methods (creator,
updater, locker).

We already use `alchemy_display_name` for the current
logged in user displayed in the admin frame.

Using this for the Page actor methods to be consistant
and allow custom user classes to present a user by it.

(cherry picked from commit 00dd34e)

app/models/alchemy/page.rb

@@ -546,7 +546,7 @@ def public_until
     # does not respond to +#name+ it returns +'unknown'+
     #
     def creator_name
-      creator.try(:name) || Alchemy.t("unknown")
+      creator.try(:alchemy_display_name) || Alchemy.t("unknown")
     end
 
     # Returns the name of the last updater of this page.
@@ -555,7 +555,7 @@ def creator_name
     # does not respond to +#name+ it returns +'unknown'+
     #
     def updater_name
-      updater.try(:name) || Alchemy.t("unknown")
+      updater.try(:alchemy_display_name) || Alchemy.t("unknown")
     end
 
     # Returns the name of the user currently editing this page.
@@ -564,7 +564,7 @@ def updater_name
     # does not respond to +#name+ it returns +'unknown'+
     #
     def locker_name
-      locker.try(:name) || Alchemy.t("unknown")
+      locker.try(:alchemy_display_name) || Alchemy.t("unknown")
     end
 
     # Key hint translations by page layout, rather than the default name.

spec/dummy/app/models/dummy_user.rb

@@ -13,13 +13,17 @@ def self.admins
   end
 
   def alchemy_roles
-    @alchemy_roles || %w(admin)
+    @alchemy_roles || %w[admin]
   end
 
   def name
     @name || email
   end
 
+  def alchemy_display_name
+    name
+  end
+
   def human_roles_string
     alchemy_roles.map(&:humanize)
   end

spec/models/alchemy/page_spec.rb

@@ -1890,7 +1890,7 @@ def copy_children_to(new_parent)
         end
       end
 
-      context "with user class having a name accessor" do
+      context "with user class having a alchemy_display_name accessor" do
         let(:user) { build(:alchemy_dummy_user, name: "Paul Page") }
 
         describe "#creator_name" do
@@ -1918,7 +1918,7 @@ def copy_children_to(new_parent)
         end
       end
 
-      context "with user class returning nil for name" do
+      context "with user class returning nil for alchemy_display_name" do
         let(:user) { Alchemy.user_class.new }
 
         describe "#creator_name" do
@@ -1946,11 +1946,11 @@ def copy_children_to(new_parent)
         end
       end
 
-      context "with user class not responding to name" do
+      context "with user class not responding to alchemy_display_name" do
         let(:user) { Alchemy.user_class.new }
 
         before do
-          expect(user).to receive(:respond_to?).with(:name) { false }
+          expect(user).to receive(:respond_to?).with(:alchemy_display_name) { false }
         end
 
         describe "#creator_name" do