DEV: ensure rebaking works even when some users have inconsistent data (#30261)

* DEV: add db consistency check for UserEmail

* DEV: add db consistency check for UserAvatar

* DEV: ignore inconsistent data related to user avatars when deciding whether to rebake old posts


Co-authored-by: Alan Guo Xiang Tan <gxtan1990@gmail.com>

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Co-authored-by: Alan Guo Xiang Tan <gxtan1990@gmail.com>

app/models/user_avatar.rb

@@ -152,6 +152,13 @@ class UserAvatar < ActiveRecord::Base
   end
 
   def self.ensure_consistency!(max_optimized_avatars_to_remove: 20_000)
+    DB.exec <<~SQL
+      DELETE FROM user_avatars
+      USING user_avatars ua
+      LEFT JOIN users u ON ua.user_id = u.id
+      WHERE user_avatars.id = ua.id AND u.id IS NULL
+    SQL
+
     DB.exec <<~SQL
       UPDATE user_avatars
       SET gravatar_upload_id = NULL