Set default of primary_key column to be unsigned.

At CNTRAL, we default our primary keys to be unsigned. As of Rails 5+, there is not clean way to do this in a monkey patch so we fork the rails repo and made this adjustment.

activerecord/lib/active_record/connection_adapters/mysql/schema_definitions.rb

@@ -77,6 +77,7 @@ def new_column_definition(name, type, **options) # :nodoc:
             type = :integer
             options[:limit] ||= 8
             options[:primary_key] = true
+            options[:unsigned] ||= true # NOTE: At CNTRAL, we default our primary keys to be unsigned. As of Rails 5+, there is not clean way to do this in a monkey patch so we fork the rails repo and made this adjustment.
           when /\Aunsigned_(?<type>.+)\z/
             type = $~[:type].to_sym
             options[:unsigned] = true