FEATURE: Let staff add custom post notices. (#7377)

db/migrate/20190414162753_rename_post_notices.rb

@@ -0,0 +1,35 @@
+class RenamePostNotices < ActiveRecord::Migration[5.2]
+  def up
+    add_index :post_custom_fields, :post_id, unique: true, name: "index_post_custom_fields_on_notice_type", where: "name = 'notice_type'"
+    add_index :post_custom_fields, :post_id, unique: true, name: "index_post_custom_fields_on_notice_args", where: "name = 'notice_args'"
+
+    # Split site setting `min_post_notice_tl` into `new_user_notice_tl` and `returning_user_notice_tl`.
+    execute <<~SQL
+      INSERT INTO site_settings(name, data_type, value, created_at, updated_at)
+      SELECT 'new_user_notice_tl', data_type, value, created_at, updated_at
+      FROM site_settings WHERE name = 'min_post_notice_tl'
+      UNION
+      SELECT 'returning_user_notice_tl', data_type, value, created_at, updated_at
+      FROM site_settings WHERE name = 'min_post_notice_tl'
+    SQL
+    execute "DELETE FROM site_settings WHERE name = 'min_post_notice_tl'"
+
+    # Rename custom fields to match new naming scheme.
+    execute "UPDATE post_custom_fields SET name = 'notice_type', value = 'new_user'       WHERE name = 'post_notice_type' AND value = 'first'"
+    execute "UPDATE post_custom_fields SET name = 'notice_type', value = 'returning_user' WHERE name = 'post_notice_type' AND value = 'returning'"
+    execute "UPDATE post_custom_fields SET name = 'notice_args'                           WHERE name = 'post_notice_time'"
+
+    # Delete all notices for bots, staged and anonymous users.
+    execute <<~SQL
+      DELETE FROM user_custom_fields
+      WHERE (name = 'notice_type' OR name = 'notice_args')
+        AND user_id IN (SELECT id FROM users WHERE id <= 0 OR staged = true
+                        UNION
+                        SELECT user_id FROM user_custom_fields ucf WHERE name = 'master_id')
+    SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end