FEATURE: Add solved icon for topic titles in search results and other topic lists

app/serializers/concerns/topic_answer_mixin.rb

@@ -0,0 +1,19 @@
+module TopicAnswerMixin
+  def self.included(klass)
+    klass.attributes :has_accepted_answer, :can_have_answer
+  end
+
+  def has_accepted_answer
+    object.custom_fields["accepted_answer_post_id"] ? true : false
+  end
+
+  def can_have_answer
+    return true if SiteSetting.allow_solved_on_all_topics
+    return false if object.closed || object.archived
+    return scope.allow_accepted_answers_on_category?(object.category_id)
+  end
+
+  def include_can_have_answer?
+    SiteSetting.empty_box_on_unsolved
+  end
+end