don't give an expired unlock-at date in lock explanation

test plan:
 - have an unpublished module with an unlock-at date in the past
 - put a file and a wiki page in it
 - as a student, ensure when you try to view these items (from the
   files and pages index pages), the "locked" message doesn't say
   they "will unlock" at a past date

fixes CNVS-28003

Change-Id: Ib02e4f78c5ea6568398c16ab18b88748068ae52f
Reviewed-on: https://gerrit.instructure.com/74695
Tested-by: Jenkins
Reviewed-by: James Williams  <jamesw@instructure.com>
QA-Review: Jahnavi Yetukuri <jyetukuri@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>

app/models/attachment.rb

@@ -1059,7 +1059,7 @@ class Attachment < ActiveRecord::Base
         locked = {:asset_string => self.asset_string, :lock_at => self.lock_at}
       elsif self.could_be_locked && item = locked_by_module_item?(user, opts[:deep_check_if_needed])
         locked = {:asset_string => self.asset_string, :context_module => item.context_module.attributes}
-        locked[:unlock_at] = locked[:context_module]["unlock_at"] if locked[:context_module]["unlock_at"]
+        locked[:unlock_at] = locked[:context_module]["unlock_at"] if locked[:context_module]["unlock_at"] && locked[:context_module]["unlock_at"] > Time.now.utc
       end
       locked
     end

app/models/wiki_page.rb

@@ -214,7 +214,7 @@ class WikiPage < ActiveRecord::Base
       locked = false
       if item = locked_by_module_item?(user, opts[:deep_check_if_needed])
         locked = {:asset_string => self.asset_string, :context_module => item.context_module.attributes}
-        locked[:unlock_at] = locked[:context_module]["unlock_at"] if locked[:context_module]["unlock_at"]
+        locked[:unlock_at] = locked[:context_module]["unlock_at"] if locked[:context_module]["unlock_at"] && locked[:context_module]["unlock_at"] > Time.now.utc
       end
       locked
     end

lib/has_content_tags.rb

@@ -44,7 +44,7 @@ module HasContentTags
   end
 
   def locked_cache_key(user)
-    keys = ['_locked_for2', self, user]
+    keys = ['_locked_for3', self, user]
     unlocked_at = self.respond_to?(:unlock_at) ? self.unlock_at : nil
     locked_at = self.respond_to?(:lock_at) ? self.lock_at : nil
     keys << (unlocked_at ? unlocked_at > Time.zone.now : false)

spec/models/wiki_page_spec.rb

@@ -506,5 +506,25 @@ describe WikiPage do
       mod.save
       expect(pageC.reload).to be_locked_for @student
     end
+
+    it "includes a future unlock date" do
+      course_with_student_logged_in active_all: true
+      page = @course.wiki.wiki_pages.create! title: 'page'
+      mod = @course.context_modules.create name: 'teh module', unlock_at: 1.week.from_now
+      mod.add_item type: 'wiki_page', id: page.id
+      mod.workflow_state = 'unpublished'
+      mod.save!
+      expect(page.reload.locked_for?(@student)[:unlock_at]).to eq mod.unlock_at
+    end
+
+    it "doesn't reference an expired unlock-at date" do
+      course_with_student_logged_in active_all: true
+      page = @course.wiki.wiki_pages.create! title: 'page'
+      mod = @course.context_modules.create name: 'teh module', unlock_at: 1.week.ago
+      mod.add_item type: 'wiki_page', id: page.id
+      mod.workflow_state = 'unpublished'
+      mod.save!
+      expect(page.reload.locked_for?(@student)).not_to have_key :unlock_at
+    end
   end
 end