Scope tags by account

We missed this one when we went to MySQL. This can results in cards tagged with cards
from other accounts. No data leaked though: the symptom is that you see the card
tagged as expected but you don't see the tag in the menu.

app/models/card/taggable.rb

@@ -9,7 +9,7 @@ module Card::Taggable
   end
 
   def toggle_tag_with(title)
-    tag = Tag.find_or_create_by!(title: title)
+    tag = account.tags.find_or_create_by!(title: title)
 
     transaction do
       if tagged_with?(tag)

test/models/card/taggable_test.rb

@@ -16,4 +16,13 @@ class Card::TaggableTest < ActiveSupport::TestCase
       @card.toggle_tag_with "ruby"
     end
   end
+
+  test "scope tags by account" do
+    assert_difference -> { Tag.count }, 2 do
+      cards(:logo).toggle_tag_with "ruby"
+      cards(:paycheck).toggle_tag_with "ruby"
+    end
+
+    assert_not_equal cards(:logo).tags.last, cards(:paycheck).tags.last
+  end
 end