DEV: Drop deprecated columns (#25640)

Since we just released 3.2, this is a good time to drop deprecated columns. This is a two-phase process. First we drop the columns, then we remove the ignored_columns declarations. Because of that I'm batching all deprecated columns for dropping here first. Once a full deploy is done we remove the declarations.

db/post_migrate/20240212034010_drop_deprecated_columns.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+class DropDeprecatedColumns < ActiveRecord::Migration[7.0]
+  DROPPED_COLUMNS ||= {
+    categories: %i[suppress_from_latest required_tag_group_id min_tags_from_required_group],
+    directory_columns: %i[automatic],
+    email_tokens: %i[token],
+    embeddable_hosts: %i[path_whitelist],
+    groups: %i[flair_url],
+    invites: %i[user_id redeemed_at],
+    posts: %i[avg_time image_url],
+    tags: %i[topic_count],
+    topic_users: %i[highest_seen_post_number],
+    topics: %i[avg_time image_url],
+    user_api_keys: %i[scopes],
+    user_options: %i[disable_jump_reply sidebar_list_destination],
+    user_profiles: %i[badge_granted_title],
+    user_stats: %i[topic_reply_count],
+  }
+
+  def up
+    DROPPED_COLUMNS.each { |table, columns| Migration::ColumnDropper.execute_drop(table, columns) }
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end