chore: Ensure null validation for private attribute in messages (#8085)

db/migrate/20231011041615_ensure_message_private_not_null.rb

@@ -0,0 +1,5 @@
+class EnsureMessagePrivateNotNull < ActiveRecord::Migration[7.0]
+  def change
+    change_column_null :messages, :private, false, false
+  end
+end