Fix: not detecting mentions when publishing saved drafts

The problem was that publishing a card with `#publish` was tracking the event
after updating the status, which was clearing the saved changes and preventing the
code from detecting the mention.

See:
https://app.fizzy.do/5986089/cards/2835

app/models/card/mentions.rb

@@ -9,7 +9,7 @@ module Card::Mentions
     end
 
     def should_check_mentions?
-      saved_change_to_status? && published?
+      was_just_published?
     end
   end
 end

app/models/card/statuses.rb

@@ -4,7 +4,10 @@ module Card::Statuses
   included do
     enum :status, %w[ drafted published ].index_by(&:itself)
 
+    attr_reader :initial_status
+
     before_save :update_created_at_on_publication
+    before_save :remember_initial_status
     after_create -> { track_event :published }, if: :published?
 
     scope :published_or_drafted_by, ->(user) { where(status: :published).or(where(status: :drafted, creator: user)) }
@@ -17,10 +20,21 @@ module Card::Statuses
     end
   end
 
+  def was_just_published?
+    initial_status&.drafted? && status_in_database.inquiry.published?
+  end
+
   private
     def update_created_at_on_publication
       if will_save_change_to_status? && status_in_database.inquiry.drafted?
         self.created_at = Time.current
       end
     end
+
+    # So that we can check it in callbacks when other operations in the transaction clean the changes.
+    def remember_initial_status
+      if will_save_change_to_status?
+        @initial_status ||= status_in_database.to_s.inquiry
+      end
+    end
 end

test/models/card/statuses_test.rb

@@ -67,4 +67,26 @@ class Card::StatusesTest < ActiveSupport::TestCase
 
     assert_equal Time.current, card.created_at
   end
+
+  test "detect drafts that were just published" do
+    Current.session = sessions(:david)
+
+    card = boards(:writebook).cards.create! creator: users(:kevin), title: "Draft Card"
+    assert card.drafted?
+    assert_not card.was_just_published?
+
+    card.publish
+
+    assert card.was_just_published?
+    assert_not Card.find(card.id).was_just_published?
+  end
+
+  test "detect cards that were created and published" do
+    Current.session = sessions(:david)
+
+    card = boards(:writebook).cards.create! creator: users(:kevin), title: "Published Card", status: :published
+    assert card.was_just_published?
+
+    assert_not Card.find(card.id).was_just_published?
+  end
 end

test/models/concerns/mentions_test.rb

@@ -23,7 +23,7 @@ class MentionsTest < ActiveSupport::TestCase
       card = Card.find(card.id)
 
       assert_difference -> { Mention.count }, +1 do
-        card.published!
+        card.publish
       end
     end
   end