feat: posts.thumbnail_base を Nullable に（#75） (#198)

Merge remote-tracking branch 'origin/main' into feature/075

#75

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #198

backend/db/migrate/20251230143400_make_thumbnail_base_nullable_in_posts.rb

@@ -0,0 +1,27 @@
+class MakeThumbnailBaseNullableInPosts < ActiveRecord::Migration[7.0]
+  def up
+    change_column_null :posts, :thumbnail_base, true
+
+    execute <<~SQL
+      UPDATE
+        posts
+      SET
+        thumbnail_base = NULL
+      WHERE
+        thumbnail_base = ''
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+      UPDATE
+        posts
+      SET
+        thumbnail_base = ''
+      WHERE
+        thumbnail_base IS NULL
+    SQL
+
+    change_column_null :posts, :thumbnail_base, false
+  end
+end