FIX: Solutions directory item was using post creation instead of solved creation (#361)

Earlier on in the migration, the update of the user directory query was erroneously switched to use post creation date instead of the date the post was solved.

This commit fixes that.

Author: nattsw

plugin.rb

@@ -295,7 +295,7 @@ def self.skip_db?
       FROM discourse_solved_solved_topics AS st
       JOIN posts AS p
          ON p.id = st.answer_post_id
-        AND COALESCE(p.created_at, :since) > :since
+        AND COALESCE(st.created_at, :since) > :since
         AND p.deleted_at IS NULL
       JOIN topics AS t
          ON t.id = st.topic_id

spec/models/directory_item_spec.rb

@@ -6,10 +6,10 @@
     fab!(:admin)
 
     fab!(:topic1) { Fabricate(:topic, archetype: "regular", user:) }
-    fab!(:topic_post1) { Fabricate(:post, topic: topic1, user:) }
+    fab!(:topic_post1) { Fabricate(:post, topic: topic1, user:, created_at: 10.years.ago) }
 
     fab!(:topic2) { Fabricate(:topic, archetype: "regular", user:) }
-    fab!(:topic_post2) { Fabricate(:post, topic: topic2, user:) }
+    fab!(:topic_post2) { Fabricate(:post, topic: topic2, user:, created_at: 10.years.ago) }
 
     fab!(:pm) { Fabricate(:topic, archetype: "private_message", user:, category_id: nil) }
     fab!(:pm_post) { Fabricate(:post, topic: pm, user:) }
@@ -97,7 +97,7 @@
       expect(
         DirectoryItem.find_by(
           user_id: user.id,
-          period_type: DirectoryItem.period_types[:all],
+          period_type: DirectoryItem.period_types[:daily],
         ).solutions,
       ).to eq(1)
     end